Merge branch 'develop' of github.com:matrix-org/synapse into erikj/dns_cache

51 files changed, 2026 insertions, 1236 deletions

diff --git a/synapse/app/homeserver.py b/synapse/app/homeserver.py
index fcdc8e6e10..2b4473b9ac 100755
--- a/synapse/app/homeserver.py
+++ b/synapse/app/homeserver.py
@@ -33,7 +33,7 @@ from synapse.python_dependencies import (
 from synapse.rest import ClientRestResource
 from synapse.storage.engines import create_engine, IncorrectDatabaseSetup
 from synapse.storage import are_all_users_on_domain
-from synapse.storage.prepare_database import UpgradeDatabaseException
+from synapse.storage.prepare_database import UpgradeDatabaseException, prepare_database
 
 from synapse.server import HomeServer
 
@@ -245,7 +245,7 @@ class SynapseHomeServer(HomeServer):
         except IncorrectDatabaseSetup as e:
             quit_with_error(e.message)
 
-    def get_db_conn(self):
+    def get_db_conn(self, run_new_connection=True):
         # Any param beginning with cp_ is a parameter for adbapi, and should
         # not be passed to the database engine.
         db_params = {
@@ -254,7 +254,8 @@ class SynapseHomeServer(HomeServer):
         }
         db_conn = self.database_engine.module.connect(**db_params)
 
-        self.database_engine.on_new_connection(db_conn)
+        if run_new_connection:
+            self.database_engine.on_new_connection(db_conn)
         return db_conn
 
 
@@ -386,7 +387,7 @@ def setup(config_options):
 
     tls_server_context_factory = context_factory.ServerContextFactory(config)
 
-    database_engine = create_engine(config)
+    database_engine = create_engine(config.database_config)
     config.database_config["args"]["cp_openfun"] = database_engine.on_new_connection
 
     hs = SynapseHomeServer(
@@ -402,8 +403,10 @@ def setup(config_options):
     logger.info("Preparing database: %s...", config.database_config['name'])
 
     try:
-        db_conn = hs.get_db_conn()
-        database_engine.prepare_database(db_conn)
+        db_conn = hs.get_db_conn(run_new_connection=False)
+        prepare_database(db_conn, database_engine, config=config)
+        database_engine.on_new_connection(db_conn)
+
         hs.run_startup_checks(db_conn, database_engine)
 
         db_conn.commit()
diff --git a/synapse/events/__init__.py b/synapse/events/__init__.py
index 925a83c645..13154b1723 100644
--- a/synapse/events/__init__.py
+++ b/synapse/events/__init__.py
@@ -33,6 +33,9 @@ class _EventInternalMetadata(object):
     def is_outlier(self):
         return getattr(self, "outlier", False)
 
+    def is_invite_from_remote(self):
+        return getattr(self, "invite_from_remote", False)
+
 
 def _event_dict_property(key):
     def getter(self):
diff --git a/synapse/handlers/__init__.py b/synapse/handlers/__init__.py
index 66d2c01123..f4dbf47c1d 100644
--- a/synapse/handlers/__init__.py
+++ b/synapse/handlers/__init__.py
@@ -17,8 +17,9 @@ from synapse.appservice.scheduler import AppServiceScheduler
 from synapse.appservice.api import ApplicationServiceApi
 from .register import RegistrationHandler
 from .room import (
-    RoomCreationHandler, RoomMemberHandler, RoomListHandler, RoomContextHandler,
+    RoomCreationHandler, RoomListHandler, RoomContextHandler,
 )
+from .room_member import RoomMemberHandler
 from .message import MessageHandler
 from .events import EventStreamHandler, EventHandler
 from .federation import FederationHandler
diff --git a/synapse/handlers/_base.py b/synapse/handlers/_base.py
index 90eabb6eb7..88d8b9ba54 100644
--- a/synapse/handlers/_base.py
+++ b/synapse/handlers/_base.py
@@ -37,12 +37,22 @@ VISIBILITY_PRIORITY = (
 )
 
 
+MEMBERSHIP_PRIORITY = (
+    Membership.JOIN,
+    Membership.INVITE,
+    Membership.KNOCK,
+    Membership.LEAVE,
+    Membership.BAN,
+)
+
+
 class BaseHandler(object):
     """
     Common base class for the event handlers.
 
-    :type store: synapse.storage.events.StateStore
-    :type state_handler: synapse.state.StateHandler
+    Attributes:
+        store (synapse.storage.events.StateStore):
+        state_handler (synapse.state.StateHandler):
     """
 
     def __init__(self, hs):
@@ -65,11 +75,13 @@ class BaseHandler(object):
         """ Returns dict of user_id -> list of events that user is allowed to
         see.
 
-        :param (str, bool) user_tuples: (user id, is_peeking) for each
-            user to be checked. is_peeking should be true if:
-              * the user is not currently a member of the room, and:
-              * the user has not been a member of the room since the given
-                events
+        Args:
+            user_tuples (str, bool): (user id, is_peeking) for each user to be
+                checked. is_peeking should be true if:
+                * the user is not currently a member of the room, and:
+                * the user has not been a member of the room since the
+                given events
+            events ([synapse.events.EventBase]): list of events to filter
         """
         forgotten = yield defer.gatherResults([
             self.store.who_forgot_in_room(
@@ -84,6 +96,12 @@ class BaseHandler(object):
         )
 
         def allowed(event, user_id, is_peeking):
+            """
+            Args:
+                event (synapse.events.EventBase): event to check
+                user_id (str)
+                is_peeking (bool)
+            """
             state = event_id_to_state[event.event_id]
 
             # get the room_visibility at the time of the event.
@@ -115,17 +133,30 @@ class BaseHandler(object):
                 if old_priority < new_priority:
                     visibility = prev_visibility
 
-            # get the user's membership at the time of the event. (or rather,
-            # just *after* the event. Which means that people can see their
-            # own join events, but not (currently) their own leave events.)
-            membership_event = state.get((EventTypes.Member, user_id), None)
-            if membership_event:
-                if membership_event.event_id in event_id_forgotten:
-                    membership = None
-                else:
-                    membership = membership_event.membership
-            else:
-                membership = None
+            # likewise, if the event is the user's own membership event, use
+            # the 'most joined' membership
+            membership = None
+            if event.type == EventTypes.Member and event.state_key == user_id:
+                membership = event.content.get("membership", None)
+                if membership not in MEMBERSHIP_PRIORITY:
+                    membership = "leave"
+
+                prev_content = event.unsigned.get("prev_content", {})
+                prev_membership = prev_content.get("membership", None)
+                if prev_membership not in MEMBERSHIP_PRIORITY:
+                    prev_membership = "leave"
+
+                new_priority = MEMBERSHIP_PRIORITY.index(membership)
+                old_priority = MEMBERSHIP_PRIORITY.index(prev_membership)
+                if old_priority < new_priority:
+                    membership = prev_membership
+
+            # otherwise, get the user's membership at the time of the event.
+            if membership is None:
+                membership_event = state.get((EventTypes.Member, user_id), None)
+                if membership_event:
+                    if membership_event.event_id not in event_id_forgotten:
+                        membership = membership_event.membership
 
             # if the user was a member of the room at the time of the event,
             # they can see it.
@@ -165,13 +196,16 @@ class BaseHandler(object):
         """
         Check which events a user is allowed to see
 
-        :param str user_id: user id to be checked
-        :param [synapse.events.EventBase] events: list of events to be checked
-        :param bool is_peeking should be True if:
+        Args:
+            user_id(str): user id to be checked
+            events([synapse.events.EventBase]): list of events to be checked
+            is_peeking(bool): should be True if:
               * the user is not currently a member of the room, and:
               * the user has not been a member of the room since the given
                 events
-        :rtype [synapse.events.EventBase]
+
+        Returns:
+            [synapse.events.EventBase]
         """
         types = (
             (EventTypes.RoomHistoryVisibility, ""),
@@ -199,20 +233,25 @@ class BaseHandler(object):
             )
 
     @defer.inlineCallbacks
-    def _create_new_client_event(self, builder):
-        latest_ret = yield self.store.get_latest_event_ids_and_hashes_in_room(
-            builder.room_id,
-        )
-
-        if latest_ret:
-            depth = max([d for _, _, d in latest_ret]) + 1
+    def _create_new_client_event(self, builder, prev_event_ids=None):
+        if prev_event_ids:
+            prev_events = yield self.store.add_event_hashes(prev_event_ids)
+            prev_max_depth = yield self.store.get_max_depth_of_events(prev_event_ids)
+            depth = prev_max_depth + 1
         else:
-            depth = 1
+            latest_ret = yield self.store.get_latest_event_ids_and_hashes_in_room(
+                builder.room_id,
+            )
 
-        prev_events = [
-            (event_id, prev_hashes)
-            for event_id, prev_hashes, _ in latest_ret
-        ]
+            if latest_ret:
+                depth = max([d for _, _, d in latest_ret]) + 1
+            else:
+                depth = 1
+
+            prev_events = [
+                (event_id, prev_hashes)
+                for event_id, prev_hashes, _ in latest_ret
+            ]
 
         builder.prev_events = prev_events
         builder.depth = depth
@@ -221,50 +260,6 @@ class BaseHandler(object):
 
         context = yield state_handler.compute_event_context(builder)
 
-        # If we've received an invite over federation, there are no latest
-        # events in the room, because we don't know enough about the graph
-        # fragment we received to treat it like a graph, so the above returned
-        # no relevant events. It may have returned some events (if we have
-        # joined and left the room), but not useful ones, like the invite.
-        if (
-            not self.is_host_in_room(context.current_state) and
-            builder.type == EventTypes.Member
-        ):
-            prev_member_event = yield self.store.get_room_member(
-                builder.sender, builder.room_id
-            )
-
-            # The prev_member_event may already be in context.current_state,
-            # despite us not being present in the room; in particular, if
-            # inviting user, and all other local users, have already left.
-            #
-            # In that case, we have all the information we need, and we don't
-            # want to drop "context" - not least because we may need to handle
-            # the invite locally, which will require us to have the whole
-            # context (not just prev_member_event) to auth it.
-            #
-            context_event_ids = (
-                e.event_id for e in context.current_state.values()
-            )
-
-            if (
-                prev_member_event and
-                prev_member_event.event_id not in context_event_ids
-            ):
-                # The prev_member_event is missing from context, so it must
-                # have arrived over federation and is an outlier. We forcibly
-                # set our context to the invite we received over federation
-                builder.prev_events = (
-                    prev_member_event.event_id,
-                    prev_member_event.prev_events
-                )
-
-                context = yield state_handler.compute_event_context(
-                    builder,
-                    old_state=(prev_member_event,),
-                    outlier=True
-                )
-
         if builder.is_state():
             builder.prev_state = yield self.store.add_event_hashes(
                 context.prev_state_events
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index 82d458b424..d5d6faa85f 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -163,9 +163,13 @@ class AuthHandler(BaseHandler):
     def get_session_id(self, clientdict):
         """
         Gets the session ID for a client given the client dictionary
-        :param clientdict: The dictionary sent by the client in the request
-        :return: The string session ID the client sent. If the client did not
-                 send a session ID, returns None.
+
+        Args:
+            clientdict: The dictionary sent by the client in the request
+
+        Returns:
+            str|None: The string session ID the client sent. If the client did
+                not send a session ID, returns None.
         """
         sid = None
         if clientdict and 'auth' in clientdict:
@@ -179,9 +183,11 @@ class AuthHandler(BaseHandler):
         Store a key-value pair into the sessions data associated with this
         request. This data is stored server-side and cannot be modified by
         the client.
-        :param session_id: (string) The ID of this session as returned from check_auth
-        :param key: (string) The key to store the data under
-        :param value: (any) The data to store
+
+        Args:
+            session_id (string): The ID of this session as returned from check_auth
+            key (string): The key to store the data under
+            value (any): The data to store
         """
         sess = self._get_session_info(session_id)
         sess.setdefault('serverdict', {})[key] = value
@@ -190,9 +196,11 @@ class AuthHandler(BaseHandler):
     def get_session_data(self, session_id, key, default=None):
         """
         Retrieve data stored with set_session_data
-        :param session_id: (string) The ID of this session as returned from check_auth
-        :param key: (string) The key to store the data under
-        :param default: (any) Value to return if the key has not been set
+
+        Args:
+            session_id (string): The ID of this session as returned from check_auth
+            key (string): The key to store the data under
+            default (any): Value to return if the key has not been set
         """
         sess = self._get_session_info(session_id)
         return sess.setdefault('serverdict', {}).get(key, default)
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 267fedf114..eb02f0e000 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -102,8 +102,7 @@ class FederationHandler(BaseHandler):
 
     @log_function
     @defer.inlineCallbacks
-    def on_receive_pdu(self, origin, pdu, state=None,
-                       auth_chain=None):
+    def on_receive_pdu(self, origin, pdu, state=None, auth_chain=None):
         """ Called by the ReplicationLayer when we have a new pdu. We need to
         do auth checks and put it through the StateHandler.
         """
@@ -174,11 +173,7 @@ class FederationHandler(BaseHandler):
                     })
                     seen_ids.add(e.event_id)
 
-                yield self._handle_new_events(
-                    origin,
-                    event_infos,
-                    outliers=True
-                )
+                yield self._handle_new_events(origin, event_infos)
 
             try:
                 context, event_stream_id, max_stream_id = yield self._handle_new_event(
@@ -289,6 +284,9 @@ class FederationHandler(BaseHandler):
     def backfill(self, dest, room_id, limit, extremities=[]):
         """ Trigger a backfill request to `dest` for the given `room_id`
         """
+        if dest == self.server_name:
+            raise SynapseError(400, "Can't backfill from self.")
+
         if not extremities:
             extremities = yield self.store.get_oldest_events_in_room(room_id)
 
@@ -455,7 +453,7 @@ class FederationHandler(BaseHandler):
 
         likely_domains = [
             domain for domain, depth in curr_domains
-            if domain is not self.server_name
+            if domain != self.server_name
         ]
 
         @defer.inlineCallbacks
@@ -761,6 +759,7 @@ class FederationHandler(BaseHandler):
         event = pdu
 
         event.internal_metadata.outlier = True
+        event.internal_metadata.invite_from_remote = True
 
         event.signatures.update(
             compute_event_signature(
@@ -788,13 +787,19 @@ class FederationHandler(BaseHandler):
 
     @defer.inlineCallbacks
     def do_remotely_reject_invite(self, target_hosts, room_id, user_id):
-        origin, event = yield self._make_and_verify_event(
-            target_hosts,
-            room_id,
-            user_id,
-            "leave"
-        )
-        signed_event = self._sign_event(event)
+        try:
+            origin, event = yield self._make_and_verify_event(
+                target_hosts,
+                room_id,
+                user_id,
+                "leave"
+            )
+            signed_event = self._sign_event(event)
+        except SynapseError:
+            raise
+        except CodeMessageException as e:
+            logger.warn("Failed to reject invite: %s", e)
+            raise SynapseError(500, "Failed to reject invite")
 
         # Try the host we successfully got a response to /make_join/
         # request first.
@@ -804,10 +809,16 @@ class FederationHandler(BaseHandler):
         except ValueError:
             pass
 
-        yield self.replication_layer.send_leave(
-            target_hosts,
-            signed_event
-        )
+        try:
+            yield self.replication_layer.send_leave(
+                target_hosts,
+                signed_event
+            )
+        except SynapseError:
+            raise
+        except CodeMessageException as e:
+            logger.warn("Failed to reject invite: %s", e)
+            raise SynapseError(500, "Failed to reject invite")
 
         context = yield self.state_handler.compute_event_context(event)
 
@@ -1069,9 +1080,6 @@ class FederationHandler(BaseHandler):
     @defer.inlineCallbacks
     @log_function
     def _handle_new_event(self, origin, event, state=None, auth_events=None):
-
-        outlier = event.internal_metadata.is_outlier()
-
         context = yield self._prep_event(
             origin, event,
             state=state,
@@ -1087,14 +1095,12 @@ class FederationHandler(BaseHandler):
         event_stream_id, max_stream_id = yield self.store.persist_event(
             event,
             context=context,
-            is_new_state=not outlier,
         )
 
         defer.returnValue((context, event_stream_id, max_stream_id))
 
     @defer.inlineCallbacks
-    def _handle_new_events(self, origin, event_infos, backfilled=False,
-                           outliers=False):
+    def _handle_new_events(self, origin, event_infos, backfilled=False):
         contexts = yield defer.gatherResults(
             [
                 self._prep_event(
@@ -1113,7 +1119,6 @@ class FederationHandler(BaseHandler):
                 for ev_info, context in itertools.izip(event_infos, contexts)
             ],
             backfilled=backfilled,
-            is_new_state=(not outliers and not backfilled),
         )
 
     @defer.inlineCallbacks
@@ -1128,11 +1133,9 @@ class FederationHandler(BaseHandler):
         """
         events_to_context = {}
         for e in itertools.chain(auth_events, state):
-            ctx = yield self.state_handler.compute_event_context(
-                e, outlier=True,
-            )
-            events_to_context[e.event_id] = ctx
             e.internal_metadata.outlier = True
+            ctx = yield self.state_handler.compute_event_context(e)
+            events_to_context[e.event_id] = ctx
 
         event_map = {
             e.event_id: e
@@ -1176,16 +1179,14 @@ class FederationHandler(BaseHandler):
                 (e, events_to_context[e.event_id])
                 for e in itertools.chain(auth_events, state)
             ],
-            is_new_state=False,
         )
 
         new_event_context = yield self.state_handler.compute_event_context(
-            event, old_state=state, outlier=False,
+            event, old_state=state
         )
 
         event_stream_id, max_stream_id = yield self.store.persist_event(
             event, new_event_context,
-            is_new_state=True,
             current_state=state,
         )
 
@@ -1193,10 +1194,9 @@ class FederationHandler(BaseHandler):
 
     @defer.inlineCallbacks
     def _prep_event(self, origin, event, state=None, auth_events=None):
-        outlier = event.internal_metadata.is_outlier()
 
         context = yield self.state_handler.compute_event_context(
-            event, old_state=state, outlier=outlier,
+            event, old_state=state,
         )
 
         if not auth_events:
@@ -1718,13 +1718,15 @@ class FederationHandler(BaseHandler):
     def _check_signature(self, event, auth_events):
         """
         Checks that the signature in the event is consistent with its invite.
-        :param event (Event): The m.room.member event to check
-        :param auth_events (dict<(event type, state_key), event>)
 
-        :raises
-            AuthError if signature didn't match any keys, or key has been
+        Args:
+            event (Event): The m.room.member event to check
+            auth_events (dict<(event type, state_key), event>):
+
+        Raises:
+            AuthError: if signature didn't match any keys, or key has been
                 revoked,
-            SynapseError if a transient error meant a key couldn't be checked
+            SynapseError: if a transient error meant a key couldn't be checked
                 for revocation.
         """
         signed = event.content["third_party_invite"]["signed"]
@@ -1766,12 +1768,13 @@ class FederationHandler(BaseHandler):
         """
         Checks whether public_key has been revoked.
 
-        :param public_key (str): base-64 encoded public key.
-        :param url (str): Key revocation URL.
+        Args:
+            public_key (str): base-64 encoded public key.
+            url (str): Key revocation URL.
 
-        :raises
-            AuthError if they key has been revoked.
-            SynapseError if a transient error meant a key couldn't be checked
+        Raises:
+            AuthError: if they key has been revoked.
+            SynapseError: if a transient error meant a key couldn't be checked
                 for revocation.
         """
         try:
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 5c50c611ba..10608c0dd9 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -21,6 +21,7 @@ from synapse.streams.config import PaginationConfig
 from synapse.events.utils import serialize_event
 from synapse.events.validator import EventValidator
 from synapse.util import unwrapFirstError
+from synapse.util.async import concurrently_execute
 from synapse.util.caches.snapshot_cache import SnapshotCache
 from synapse.types import UserID, RoomStreamToken, StreamToken
 
@@ -175,7 +176,7 @@ class MessageHandler(BaseHandler):
         defer.returnValue(chunk)
 
     @defer.inlineCallbacks
-    def create_event(self, event_dict, token_id=None, txn_id=None):
+    def create_event(self, event_dict, token_id=None, txn_id=None, prev_event_ids=None):
         """
         Given a dict from a client, create a new event.
 
@@ -186,6 +187,9 @@ class MessageHandler(BaseHandler):
 
         Args:
             event_dict (dict): An entire event
+            token_id (str)
+            txn_id (str)
+            prev_event_ids (list): The prev event ids to use when creating the event
 
         Returns:
             Tuple of created event (FrozenEvent), Context
@@ -224,6 +228,7 @@ class MessageHandler(BaseHandler):
 
         event, context = yield self._create_new_client_event(
             builder=builder,
+            prev_event_ids=prev_event_ids,
         )
         defer.returnValue((event, context))
 
@@ -556,14 +561,7 @@ class MessageHandler(BaseHandler):
             except:
                 logger.exception("Failed to get snapshot")
 
-        # Only do N rooms at once
-        n = 5
-        d_list = [handle_room(e) for e in room_list]
-        for i in range(0, len(d_list), n):
-            yield defer.gatherResults(
-                d_list[i:i + n],
-                consumeErrors=True
-            ).addErrback(unwrapFirstError)
+        yield concurrently_execute(handle_room, room_list, 10)
 
         account_data_events = []
         for account_data_type, content in account_data.items():
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 71f7ab3d22..3e1d9282d7 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -18,20 +18,17 @@ from twisted.internet import defer
 
 from ._base import BaseHandler
 
-from synapse.types import UserID, RoomAlias, RoomID, RoomStreamToken, Requester
+from synapse.types import UserID, RoomAlias, RoomID, RoomStreamToken
 from synapse.api.constants import (
-    EventTypes, Membership, JoinRules, RoomCreationPreset,
+    EventTypes, JoinRules, RoomCreationPreset,
 )
-from synapse.api.errors import AuthError, StoreError, SynapseError, Codes
-from synapse.util import stringutils, unwrapFirstError
+from synapse.api.errors import AuthError, StoreError, SynapseError
+from synapse.util import stringutils
+from synapse.util.async import concurrently_execute
 from synapse.util.logcontext import preserve_context_over_fn
 from synapse.util.caches.response_cache import ResponseCache
 
-from signedjson.sign import verify_signed_json
-from signedjson.key import decode_verify_key_bytes
-
 from collections import OrderedDict
-from unpaddedbase64 import decode_base64
 
 import logging
 import math
@@ -357,599 +354,6 @@ class RoomCreationHandler(BaseHandler):
             )
 
 
-class RoomMemberHandler(BaseHandler):
-    # TODO(paul): This handler currently contains a messy conflation of
-    #   low-level API that works on UserID objects and so on, and REST-level
-    #   API that takes ID strings and returns pagination chunks. These concerns
-    #   ought to be separated out a lot better.
-
-    def __init__(self, hs):
-        super(RoomMemberHandler, self).__init__(hs)
-
-        self.clock = hs.get_clock()
-
-        self.distributor = hs.get_distributor()
-        self.distributor.declare("user_joined_room")
-        self.distributor.declare("user_left_room")
-
-    @defer.inlineCallbacks
-    def get_room_members(self, room_id):
-        users = yield self.store.get_users_in_room(room_id)
-
-        defer.returnValue([UserID.from_string(u) for u in users])
-
-    @defer.inlineCallbacks
-    def fetch_room_distributions_into(self, room_id, localusers=None,
-                                      remotedomains=None, ignore_user=None):
-        """Fetch the distribution of a room, adding elements to either
-        'localusers' or 'remotedomains', which should be a set() if supplied.
-        If ignore_user is set, ignore that user.
-
-        This function returns nothing; its result is performed by the
-        side-effect on the two passed sets. This allows easy accumulation of
-        member lists of multiple rooms at once if required.
-        """
-        members = yield self.get_room_members(room_id)
-        for member in members:
-            if ignore_user is not None and member == ignore_user:
-                continue
-
-            if self.hs.is_mine(member):
-                if localusers is not None:
-                    localusers.add(member)
-            else:
-                if remotedomains is not None:
-                    remotedomains.add(member.domain)
-
-    @defer.inlineCallbacks
-    def update_membership(
-            self,
-            requester,
-            target,
-            room_id,
-            action,
-            txn_id=None,
-            remote_room_hosts=None,
-            third_party_signed=None,
-            ratelimit=True,
-    ):
-        effective_membership_state = action
-        if action in ["kick", "unban"]:
-            effective_membership_state = "leave"
-
-        if third_party_signed is not None:
-            replication = self.hs.get_replication_layer()
-            yield replication.exchange_third_party_invite(
-                third_party_signed["sender"],
-                target.to_string(),
-                room_id,
-                third_party_signed,
-            )
-
-        msg_handler = self.hs.get_handlers().message_handler
-
-        content = {"membership": effective_membership_state}
-        if requester.is_guest:
-            content["kind"] = "guest"
-
-        event, context = yield msg_handler.create_event(
-            {
-                "type": EventTypes.Member,
-                "content": content,
-                "room_id": room_id,
-                "sender": requester.user.to_string(),
-                "state_key": target.to_string(),
-
-                # For backwards compatibility:
-                "membership": effective_membership_state,
-            },
-            token_id=requester.access_token_id,
-            txn_id=txn_id,
-        )
-
-        old_state = context.current_state.get((EventTypes.Member, event.state_key))
-        old_membership = old_state.content.get("membership") if old_state else None
-        if action == "unban" and old_membership != "ban":
-            raise SynapseError(
-                403,
-                "Cannot unban user who was not banned (membership=%s)" % old_membership,
-                errcode=Codes.BAD_STATE
-            )
-        if old_membership == "ban" and action != "unban":
-            raise SynapseError(
-                403,
-                "Cannot %s user who was is banned" % (action,),
-                errcode=Codes.BAD_STATE
-            )
-
-        member_handler = self.hs.get_handlers().room_member_handler
-        yield member_handler.send_membership_event(
-            requester,
-            event,
-            context,
-            ratelimit=ratelimit,
-            remote_room_hosts=remote_room_hosts,
-        )
-
-    @defer.inlineCallbacks
-    def send_membership_event(
-            self,
-            requester,
-            event,
-            context,
-            remote_room_hosts=None,
-            ratelimit=True,
-    ):
-        """
-        Change the membership status of a user in a room.
-
-        Args:
-            requester (Requester): The local user who requested the membership
-                event. If None, certain checks, like whether this homeserver can
-                act as the sender, will be skipped.
-            event (SynapseEvent): The membership event.
-            context: The context of the event.
-            is_guest (bool): Whether the sender is a guest.
-            room_hosts ([str]): Homeservers which are likely to already be in
-                the room, and could be danced with in order to join this
-                homeserver for the first time.
-            ratelimit (bool): Whether to rate limit this request.
-        Raises:
-            SynapseError if there was a problem changing the membership.
-        """
-        remote_room_hosts = remote_room_hosts or []
-
-        target_user = UserID.from_string(event.state_key)
-        room_id = event.room_id
-
-        if requester is not None:
-            sender = UserID.from_string(event.sender)
-            assert sender == requester.user, (
-                "Sender (%s) must be same as requester (%s)" %
-                (sender, requester.user)
-            )
-            assert self.hs.is_mine(sender), "Sender must be our own: %s" % (sender,)
-        else:
-            requester = Requester(target_user, None, False)
-
-        message_handler = self.hs.get_handlers().message_handler
-        prev_event = message_handler.deduplicate_state_event(event, context)
-        if prev_event is not None:
-            return
-
-        action = "send"
-
-        if event.membership == Membership.JOIN:
-            if requester.is_guest and not self._can_guest_join(context.current_state):
-                # This should be an auth check, but guests are a local concept,
-                # so don't really fit into the general auth process.
-                raise AuthError(403, "Guest access not allowed")
-            do_remote_join_dance, remote_room_hosts = self._should_do_dance(
-                context,
-                (self.get_inviter(event.state_key, context.current_state)),
-                remote_room_hosts,
-            )
-            if do_remote_join_dance:
-                action = "remote_join"
-        elif event.membership == Membership.LEAVE:
-            is_host_in_room = self.is_host_in_room(context.current_state)
-
-            if not is_host_in_room:
-                # perhaps we've been invited
-                inviter = self.get_inviter(target_user.to_string(), context.current_state)
-                if not inviter:
-                    raise SynapseError(404, "Not a known room")
-
-                if self.hs.is_mine(inviter):
-                    # the inviter was on our server, but has now left. Carry on
-                    # with the normal rejection codepath.
-                    #
-                    # This is a bit of a hack, because the room might still be
-                    # active on other servers.
-                    pass
-                else:
-                    # send the rejection to the inviter's HS.
-                    remote_room_hosts = remote_room_hosts + [inviter.domain]
-                    action = "remote_reject"
-
-        federation_handler = self.hs.get_handlers().federation_handler
-
-        if action == "remote_join":
-            if len(remote_room_hosts) == 0:
-                raise SynapseError(404, "No known servers")
-
-            # We don't do an auth check if we are doing an invite
-            # join dance for now, since we're kinda implicitly checking
-            # that we are allowed to join when we decide whether or not we
-            # need to do the invite/join dance.
-            yield federation_handler.do_invite_join(
-                remote_room_hosts,
-                event.room_id,
-                event.user_id,
-                event.content,
-            )
-        elif action == "remote_reject":
-            yield federation_handler.do_remotely_reject_invite(
-                remote_room_hosts,
-                room_id,
-                event.user_id
-            )
-        else:
-            yield self.handle_new_client_event(
-                requester,
-                event,
-                context,
-                extra_users=[target_user],
-                ratelimit=ratelimit,
-            )
-
-        prev_member_event = context.current_state.get(
-            (EventTypes.Member, target_user.to_string()),
-            None
-        )
-
-        if event.membership == Membership.JOIN:
-            if not prev_member_event or prev_member_event.membership != Membership.JOIN:
-                # Only fire user_joined_room if the user has acutally joined the
-                # room. Don't bother if the user is just changing their profile
-                # info.
-                yield user_joined_room(self.distributor, target_user, room_id)
-        elif event.membership == Membership.LEAVE:
-            if prev_member_event and prev_member_event.membership == Membership.JOIN:
-                user_left_room(self.distributor, target_user, room_id)
-
-    def _can_guest_join(self, current_state):
-        """
-        Returns whether a guest can join a room based on its current state.
-        """
-        guest_access = current_state.get((EventTypes.GuestAccess, ""), None)
-        return (
-            guest_access
-            and guest_access.content
-            and "guest_access" in guest_access.content
-            and guest_access.content["guest_access"] == "can_join"
-        )
-
-    def _should_do_dance(self, context, inviter, room_hosts=None):
-        # TODO: Shouldn't this be remote_room_host?
-        room_hosts = room_hosts or []
-
-        is_host_in_room = self.is_host_in_room(context.current_state)
-        if is_host_in_room:
-            return False, room_hosts
-
-        if inviter and not self.hs.is_mine(inviter):
-            room_hosts.append(inviter.domain)
-
-        return True, room_hosts
-
-    @defer.inlineCallbacks
-    def lookup_room_alias(self, room_alias):
-        """
-        Get the room ID associated with a room alias.
-
-        Args:
-            room_alias (RoomAlias): The alias to look up.
-        Returns:
-            A tuple of:
-                The room ID as a RoomID object.
-                Hosts likely to be participating in the room ([str]).
-        Raises:
-            SynapseError if room alias could not be found.
-        """
-        directory_handler = self.hs.get_handlers().directory_handler
-        mapping = yield directory_handler.get_association(room_alias)
-
-        if not mapping:
-            raise SynapseError(404, "No such room alias")
-
-        room_id = mapping["room_id"]
-        servers = mapping["servers"]
-
-        defer.returnValue((RoomID.from_string(room_id), servers))
-
-    def get_inviter(self, user_id, current_state):
-        prev_state = current_state.get((EventTypes.Member, user_id))
-        if prev_state and prev_state.membership == Membership.INVITE:
-            return UserID.from_string(prev_state.user_id)
-        return None
-
-    @defer.inlineCallbacks
-    def get_joined_rooms_for_user(self, user):
-        """Returns a list of roomids that the user has any of the given
-        membership states in."""
-
-        rooms = yield self.store.get_rooms_for_user(
-            user.to_string(),
-        )
-
-        # For some reason the list of events contains duplicates
-        # TODO(paul): work out why because I really don't think it should
-        room_ids = set(r.room_id for r in rooms)
-
-        defer.returnValue(room_ids)
-
-    @defer.inlineCallbacks
-    def do_3pid_invite(
-            self,
-            room_id,
-            inviter,
-            medium,
-            address,
-            id_server,
-            requester,
-            txn_id
-    ):
-        invitee = yield self._lookup_3pid(
-            id_server, medium, address
-        )
-
-        if invitee:
-            handler = self.hs.get_handlers().room_member_handler
-            yield handler.update_membership(
-                requester,
-                UserID.from_string(invitee),
-                room_id,
-                "invite",
-                txn_id=txn_id,
-            )
-        else:
-            yield self._make_and_store_3pid_invite(
-                requester,
-                id_server,
-                medium,
-                address,
-                room_id,
-                inviter,
-                txn_id=txn_id
-            )
-
-    @defer.inlineCallbacks
-    def _lookup_3pid(self, id_server, medium, address):
-        """Looks up a 3pid in the passed identity server.
-
-        Args:
-            id_server (str): The server name (including port, if required)
-                of the identity server to use.
-            medium (str): The type of the third party identifier (e.g. "email").
-            address (str): The third party identifier (e.g. "foo@example.com").
-
-        Returns:
-            (str) the matrix ID of the 3pid, or None if it is not recognized.
-        """
-        try:
-            data = yield self.hs.get_simple_http_client().get_json(
-                "%s%s/_matrix/identity/api/v1/lookup" % (id_server_scheme, id_server,),
-                {
-                    "medium": medium,
-                    "address": address,
-                }
-            )
-
-            if "mxid" in data:
-                if "signatures" not in data:
-                    raise AuthError(401, "No signatures on 3pid binding")
-                self.verify_any_signature(data, id_server)
-                defer.returnValue(data["mxid"])
-
-        except IOError as e:
-            logger.warn("Error from identity server lookup: %s" % (e,))
-            defer.returnValue(None)
-
-    @defer.inlineCallbacks
-    def verify_any_signature(self, data, server_hostname):
-        if server_hostname not in data["signatures"]:
-            raise AuthError(401, "No signature from server %s" % (server_hostname,))
-        for key_name, signature in data["signatures"][server_hostname].items():
-            key_data = yield self.hs.get_simple_http_client().get_json(
-                "%s%s/_matrix/identity/api/v1/pubkey/%s" %
-                (id_server_scheme, server_hostname, key_name,),
-            )
-            if "public_key" not in key_data:
-                raise AuthError(401, "No public key named %s from %s" %
-                                (key_name, server_hostname,))
-            verify_signed_json(
-                data,
-                server_hostname,
-                decode_verify_key_bytes(key_name, decode_base64(key_data["public_key"]))
-            )
-            return
-
-    @defer.inlineCallbacks
-    def _make_and_store_3pid_invite(
-            self,
-            requester,
-            id_server,
-            medium,
-            address,
-            room_id,
-            user,
-            txn_id
-    ):
-        room_state = yield self.hs.get_state_handler().get_current_state(room_id)
-
-        inviter_display_name = ""
-        inviter_avatar_url = ""
-        member_event = room_state.get((EventTypes.Member, user.to_string()))
-        if member_event:
-            inviter_display_name = member_event.content.get("displayname", "")
-            inviter_avatar_url = member_event.content.get("avatar_url", "")
-
-        canonical_room_alias = ""
-        canonical_alias_event = room_state.get((EventTypes.CanonicalAlias, ""))
-        if canonical_alias_event:
-            canonical_room_alias = canonical_alias_event.content.get("alias", "")
-
-        room_name = ""
-        room_name_event = room_state.get((EventTypes.Name, ""))
-        if room_name_event:
-            room_name = room_name_event.content.get("name", "")
-
-        room_join_rules = ""
-        join_rules_event = room_state.get((EventTypes.JoinRules, ""))
-        if join_rules_event:
-            room_join_rules = join_rules_event.content.get("join_rule", "")
-
-        room_avatar_url = ""
-        room_avatar_event = room_state.get((EventTypes.RoomAvatar, ""))
-        if room_avatar_event:
-            room_avatar_url = room_avatar_event.content.get("url", "")
-
-        token, public_keys, fallback_public_key, display_name = (
-            yield self._ask_id_server_for_third_party_invite(
-                id_server=id_server,
-                medium=medium,
-                address=address,
-                room_id=room_id,
-                inviter_user_id=user.to_string(),
-                room_alias=canonical_room_alias,
-                room_avatar_url=room_avatar_url,
-                room_join_rules=room_join_rules,
-                room_name=room_name,
-                inviter_display_name=inviter_display_name,
-                inviter_avatar_url=inviter_avatar_url
-            )
-        )
-
-        msg_handler = self.hs.get_handlers().message_handler
-        yield msg_handler.create_and_send_nonmember_event(
-            requester,
-            {
-                "type": EventTypes.ThirdPartyInvite,
-                "content": {
-                    "display_name": display_name,
-                    "public_keys": public_keys,
-
-                    # For backwards compatibility:
-                    "key_validity_url": fallback_public_key["key_validity_url"],
-                    "public_key": fallback_public_key["public_key"],
-                },
-                "room_id": room_id,
-                "sender": user.to_string(),
-                "state_key": token,
-            },
-            txn_id=txn_id,
-        )
-
-    @defer.inlineCallbacks
-    def _ask_id_server_for_third_party_invite(
-            self,
-            id_server,
-            medium,
-            address,
-            room_id,
-            inviter_user_id,
-            room_alias,
-            room_avatar_url,
-            room_join_rules,
-            room_name,
-            inviter_display_name,
-            inviter_avatar_url
-    ):
-        """
-        Asks an identity server for a third party invite.
-
-        :param id_server (str): hostname + optional port for the identity server.
-        :param medium (str): The literal string "email".
-        :param address (str): The third party address being invited.
-        :param room_id (str): The ID of the room to which the user is invited.
-        :param inviter_user_id (str): The user ID of the inviter.
-        :param room_alias (str): An alias for the room, for cosmetic
-            notifications.
-        :param room_avatar_url (str): The URL of the room's avatar, for cosmetic
-            notifications.
-        :param room_join_rules (str): The join rules of the email
-            (e.g. "public").
-        :param room_name (str): The m.room.name of the room.
-        :param inviter_display_name (str): The current display name of the
-            inviter.
-        :param inviter_avatar_url (str): The URL of the inviter's avatar.
-
-        :return: A deferred tuple containing:
-            token (str): The token which must be signed to prove authenticity.
-            public_keys ([{"public_key": str, "key_validity_url": str}]):
-                public_key is a base64-encoded ed25519 public key.
-            fallback_public_key: One element from public_keys.
-            display_name (str): A user-friendly name to represent the invited
-                user.
-        """
-
-        is_url = "%s%s/_matrix/identity/api/v1/store-invite" % (
-            id_server_scheme, id_server,
-        )
-
-        invite_config = {
-            "medium": medium,
-            "address": address,
-            "room_id": room_id,
-            "room_alias": room_alias,
-            "room_avatar_url": room_avatar_url,
-            "room_join_rules": room_join_rules,
-            "room_name": room_name,
-            "sender": inviter_user_id,
-            "sender_display_name": inviter_display_name,
-            "sender_avatar_url": inviter_avatar_url,
-        }
-
-        if self.hs.config.invite_3pid_guest:
-            registration_handler = self.hs.get_handlers().registration_handler
-            guest_access_token = yield registration_handler.guest_access_token_for(
-                medium=medium,
-                address=address,
-                inviter_user_id=inviter_user_id,
-            )
-
-            guest_user_info = yield self.hs.get_auth().get_user_by_access_token(
-                guest_access_token
-            )
-
-            invite_config.update({
-                "guest_access_token": guest_access_token,
-                "guest_user_id": guest_user_info["user"].to_string(),
-            })
-
-        data = yield self.hs.get_simple_http_client().post_urlencoded_get_json(
-            is_url,
-            invite_config
-        )
-        # TODO: Check for success
-        token = data["token"]
-        public_keys = data.get("public_keys", [])
-        if "public_key" in data:
-            fallback_public_key = {
-                "public_key": data["public_key"],
-                "key_validity_url": "%s%s/_matrix/identity/api/v1/pubkey/isvalid" % (
-                    id_server_scheme, id_server,
-                ),
-            }
-        else:
-            fallback_public_key = public_keys[0]
-
-        if not public_keys:
-            public_keys.append(fallback_public_key)
-        display_name = data["display_name"]
-        defer.returnValue((token, public_keys, fallback_public_key, display_name))
-
-    @defer.inlineCallbacks
-    def forget(self, user, room_id):
-        user_id = user.to_string()
-
-        member = yield self.state_handler.get_current_state(
-            room_id=room_id,
-            event_type=EventTypes.Member,
-            state_key=user_id
-        )
-        membership = member.membership if member else None
-
-        if membership is not None and membership != Membership.LEAVE:
-            raise SynapseError(400, "User %s in room %s" % (
-                user_id, room_id
-            ))
-
-        if membership:
-            yield self.store.forget(user_id, room_id)
-
-
 class RoomListHandler(BaseHandler):
     def __init__(self, hs):
         super(RoomListHandler, self).__init__(hs)
@@ -965,6 +369,8 @@ class RoomListHandler(BaseHandler):
     def _get_public_room_list(self):
         room_ids = yield self.store.get_public_room_ids()
 
+        results = []
+
         @defer.inlineCallbacks
         def handle_room(room_id):
             aliases = yield self.store.get_aliases_for_room(room_id)
@@ -1025,18 +431,12 @@ class RoomListHandler(BaseHandler):
             joined_users = yield self.store.get_users_in_room(room_id)
             result["num_joined_members"] = len(joined_users)
 
-            defer.returnValue(result)
+            results.append(result)
 
-        result = []
-        for chunk in (room_ids[i:i + 10] for i in xrange(0, len(room_ids), 10)):
-            chunk_result = yield defer.gatherResults([
-                handle_room(room_id)
-                for room_id in chunk
-            ], consumeErrors=True).addErrback(unwrapFirstError)
-            result.extend(v for v in chunk_result if v)
+        yield concurrently_execute(handle_room, room_ids, 10)
 
         # FIXME (erikj): START is no longer a valid value
-        defer.returnValue({"start": "START", "end": "END", "chunk": result})
+        defer.returnValue({"start": "START", "end": "END", "chunk": results})
 
 
 class RoomContextHandler(BaseHandler):
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
new file mode 100644
index 0000000000..8c41cb6f3c
--- /dev/null
+++ b/synapse/handlers/room_member.py
@@ -0,0 +1,718 @@
+# -*- coding: utf-8 -*-
+# Copyright 2016 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+from twisted.internet import defer
+
+from ._base import BaseHandler
+
+from synapse.types import UserID, RoomID, Requester
+from synapse.api.constants import (
+    EventTypes, Membership,
+)
+from synapse.api.errors import AuthError, SynapseError, Codes
+from synapse.util.logcontext import preserve_context_over_fn
+
+from signedjson.sign import verify_signed_json
+from signedjson.key import decode_verify_key_bytes
+
+from unpaddedbase64 import decode_base64
+
+import logging
+
+logger = logging.getLogger(__name__)
+
+id_server_scheme = "https://"
+
+
+def user_left_room(distributor, user, room_id):
+    return preserve_context_over_fn(
+        distributor.fire,
+        "user_left_room", user=user, room_id=room_id
+    )
+
+
+def user_joined_room(distributor, user, room_id):
+    return preserve_context_over_fn(
+        distributor.fire,
+        "user_joined_room", user=user, room_id=room_id
+    )
+
+
+class RoomMemberHandler(BaseHandler):
+    # TODO(paul): This handler currently contains a messy conflation of
+    #   low-level API that works on UserID objects and so on, and REST-level
+    #   API that takes ID strings and returns pagination chunks. These concerns
+    #   ought to be separated out a lot better.
+
+    def __init__(self, hs):
+        super(RoomMemberHandler, self).__init__(hs)
+
+        self.clock = hs.get_clock()
+
+        self.distributor = hs.get_distributor()
+        self.distributor.declare("user_joined_room")
+        self.distributor.declare("user_left_room")
+
+    @defer.inlineCallbacks
+    def get_room_members(self, room_id):
+        users = yield self.store.get_users_in_room(room_id)
+
+        defer.returnValue([UserID.from_string(u) for u in users])
+
+    @defer.inlineCallbacks
+    def fetch_room_distributions_into(self, room_id, localusers=None,
+                                      remotedomains=None, ignore_user=None):
+        """Fetch the distribution of a room, adding elements to either
+        'localusers' or 'remotedomains', which should be a set() if supplied.
+        If ignore_user is set, ignore that user.
+
+        This function returns nothing; its result is performed by the
+        side-effect on the two passed sets. This allows easy accumulation of
+        member lists of multiple rooms at once if required.
+        """
+        members = yield self.get_room_members(room_id)
+        for member in members:
+            if ignore_user is not None and member == ignore_user:
+                continue
+
+            if self.hs.is_mine(member):
+                if localusers is not None:
+                    localusers.add(member)
+            else:
+                if remotedomains is not None:
+                    remotedomains.add(member.domain)
+
+    @defer.inlineCallbacks
+    def _local_membership_update(
+        self, requester, target, room_id, membership,
+        prev_event_ids,
+        txn_id=None,
+        ratelimit=True,
+    ):
+        msg_handler = self.hs.get_handlers().message_handler
+
+        content = {"membership": membership}
+        if requester.is_guest:
+            content["kind"] = "guest"
+
+        event, context = yield msg_handler.create_event(
+            {
+                "type": EventTypes.Member,
+                "content": content,
+                "room_id": room_id,
+                "sender": requester.user.to_string(),
+                "state_key": target.to_string(),
+
+                # For backwards compatibility:
+                "membership": membership,
+            },
+            token_id=requester.access_token_id,
+            txn_id=txn_id,
+            prev_event_ids=prev_event_ids,
+        )
+
+        yield self.handle_new_client_event(
+            requester,
+            event,
+            context,
+            extra_users=[target],
+            ratelimit=ratelimit,
+        )
+
+        prev_member_event = context.current_state.get(
+            (EventTypes.Member, target.to_string()),
+            None
+        )
+
+        if event.membership == Membership.JOIN:
+            if not prev_member_event or prev_member_event.membership != Membership.JOIN:
+                # Only fire user_joined_room if the user has acutally joined the
+                # room. Don't bother if the user is just changing their profile
+                # info.
+                yield user_joined_room(self.distributor, target, room_id)
+        elif event.membership == Membership.LEAVE:
+            if prev_member_event and prev_member_event.membership == Membership.JOIN:
+                user_left_room(self.distributor, target, room_id)
+
+    @defer.inlineCallbacks
+    def remote_join(self, remote_room_hosts, room_id, user, content):
+        if len(remote_room_hosts) == 0:
+            raise SynapseError(404, "No known servers")
+
+        # We don't do an auth check if we are doing an invite
+        # join dance for now, since we're kinda implicitly checking
+        # that we are allowed to join when we decide whether or not we
+        # need to do the invite/join dance.
+        yield self.hs.get_handlers().federation_handler.do_invite_join(
+            remote_room_hosts,
+            room_id,
+            user.to_string(),
+            content,
+        )
+        yield user_joined_room(self.distributor, user, room_id)
+
+    def reject_remote_invite(self, user_id, room_id, remote_room_hosts):
+        return self.hs.get_handlers().federation_handler.do_remotely_reject_invite(
+            remote_room_hosts,
+            room_id,
+            user_id
+        )
+
+    @defer.inlineCallbacks
+    def update_membership(
+            self,
+            requester,
+            target,
+            room_id,
+            action,
+            txn_id=None,
+            remote_room_hosts=None,
+            third_party_signed=None,
+            ratelimit=True,
+    ):
+        effective_membership_state = action
+        if action in ["kick", "unban"]:
+            effective_membership_state = "leave"
+
+        if third_party_signed is not None:
+            replication = self.hs.get_replication_layer()
+            yield replication.exchange_third_party_invite(
+                third_party_signed["sender"],
+                target.to_string(),
+                room_id,
+                third_party_signed,
+            )
+
+        if not remote_room_hosts:
+            remote_room_hosts = []
+
+        latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
+        current_state = yield self.state_handler.get_current_state(
+            room_id, latest_event_ids=latest_event_ids,
+        )
+
+        old_state = current_state.get((EventTypes.Member, target.to_string()))
+        old_membership = old_state.content.get("membership") if old_state else None
+        if action == "unban" and old_membership != "ban":
+            raise SynapseError(
+                403,
+                "Cannot unban user who was not banned (membership=%s)" % old_membership,
+                errcode=Codes.BAD_STATE
+            )
+        if old_membership == "ban" and action != "unban":
+            raise SynapseError(
+                403,
+                "Cannot %s user who was is banned" % (action,),
+                errcode=Codes.BAD_STATE
+            )
+
+        is_host_in_room = self.is_host_in_room(current_state)
+
+        if effective_membership_state == Membership.JOIN:
+            if requester.is_guest and not self._can_guest_join(current_state):
+                # This should be an auth check, but guests are a local concept,
+                # so don't really fit into the general auth process.
+                raise AuthError(403, "Guest access not allowed")
+
+            if not is_host_in_room:
+                inviter = yield self.get_inviter(target.to_string(), room_id)
+                if inviter and not self.hs.is_mine(inviter):
+                    remote_room_hosts.append(inviter.domain)
+
+                content = {"membership": Membership.JOIN}
+
+                profile = self.hs.get_handlers().profile_handler
+                content["displayname"] = yield profile.get_displayname(target)
+                content["avatar_url"] = yield profile.get_avatar_url(target)
+
+                if requester.is_guest:
+                    content["kind"] = "guest"
+
+                ret = yield self.remote_join(
+                    remote_room_hosts, room_id, target, content
+                )
+                defer.returnValue(ret)
+
+        elif effective_membership_state == Membership.LEAVE:
+            if not is_host_in_room:
+                # perhaps we've been invited
+                inviter = yield self.get_inviter(target.to_string(), room_id)
+                if not inviter:
+                    raise SynapseError(404, "Not a known room")
+
+                if self.hs.is_mine(inviter):
+                    # the inviter was on our server, but has now left. Carry on
+                    # with the normal rejection codepath.
+                    #
+                    # This is a bit of a hack, because the room might still be
+                    # active on other servers.
+                    pass
+                else:
+                    # send the rejection to the inviter's HS.
+                    remote_room_hosts = remote_room_hosts + [inviter.domain]
+
+                    try:
+                        ret = yield self.reject_remote_invite(
+                            target.to_string(), room_id, remote_room_hosts
+                        )
+                        defer.returnValue(ret)
+                    except SynapseError as e:
+                        logger.warn("Failed to reject invite: %s", e)
+
+                        yield self.store.locally_reject_invite(
+                            target.to_string(), room_id
+                        )
+
+                        defer.returnValue({})
+
+        yield self._local_membership_update(
+            requester=requester,
+            target=target,
+            room_id=room_id,
+            membership=effective_membership_state,
+            txn_id=txn_id,
+            ratelimit=ratelimit,
+            prev_event_ids=latest_event_ids,
+        )
+
+    @defer.inlineCallbacks
+    def send_membership_event(
+            self,
+            requester,
+            event,
+            context,
+            remote_room_hosts=None,
+            ratelimit=True,
+    ):
+        """
+        Change the membership status of a user in a room.
+
+        Args:
+            requester (Requester): The local user who requested the membership
+                event. If None, certain checks, like whether this homeserver can
+                act as the sender, will be skipped.
+            event (SynapseEvent): The membership event.
+            context: The context of the event.
+            is_guest (bool): Whether the sender is a guest.
+            room_hosts ([str]): Homeservers which are likely to already be in
+                the room, and could be danced with in order to join this
+                homeserver for the first time.
+            ratelimit (bool): Whether to rate limit this request.
+        Raises:
+            SynapseError if there was a problem changing the membership.
+        """
+        remote_room_hosts = remote_room_hosts or []
+
+        target_user = UserID.from_string(event.state_key)
+        room_id = event.room_id
+
+        if requester is not None:
+            sender = UserID.from_string(event.sender)
+            assert sender == requester.user, (
+                "Sender (%s) must be same as requester (%s)" %
+                (sender, requester.user)
+            )
+            assert self.hs.is_mine(sender), "Sender must be our own: %s" % (sender,)
+        else:
+            requester = Requester(target_user, None, False)
+
+        message_handler = self.hs.get_handlers().message_handler
+        prev_event = message_handler.deduplicate_state_event(event, context)
+        if prev_event is not None:
+            return
+
+        if event.membership == Membership.JOIN:
+            if requester.is_guest and not self._can_guest_join(context.current_state):
+                # This should be an auth check, but guests are a local concept,
+                # so don't really fit into the general auth process.
+                raise AuthError(403, "Guest access not allowed")
+
+        yield self.handle_new_client_event(
+            requester,
+            event,
+            context,
+            extra_users=[target_user],
+            ratelimit=ratelimit,
+        )
+
+        prev_member_event = context.current_state.get(
+            (EventTypes.Member, target_user.to_string()),
+            None
+        )
+
+        if event.membership == Membership.JOIN:
+            if not prev_member_event or prev_member_event.membership != Membership.JOIN:
+                # Only fire user_joined_room if the user has acutally joined the
+                # room. Don't bother if the user is just changing their profile
+                # info.
+                yield user_joined_room(self.distributor, target_user, room_id)
+        elif event.membership == Membership.LEAVE:
+            if prev_member_event and prev_member_event.membership == Membership.JOIN:
+                user_left_room(self.distributor, target_user, room_id)
+
+    def _can_guest_join(self, current_state):
+        """
+        Returns whether a guest can join a room based on its current state.
+        """
+        guest_access = current_state.get((EventTypes.GuestAccess, ""), None)
+        return (
+            guest_access
+            and guest_access.content
+            and "guest_access" in guest_access.content
+            and guest_access.content["guest_access"] == "can_join"
+        )
+
+    def _should_do_dance(self, current_state, inviter, room_hosts=None):
+        # TODO: Shouldn't this be remote_room_host?
+        room_hosts = room_hosts or []
+
+        is_host_in_room = self.is_host_in_room(current_state)
+        if is_host_in_room:
+            return False, room_hosts
+
+        if inviter and not self.hs.is_mine(inviter):
+            room_hosts.append(inviter.domain)
+
+        return True, room_hosts
+
+    @defer.inlineCallbacks
+    def lookup_room_alias(self, room_alias):
+        """
+        Get the room ID associated with a room alias.
+
+        Args:
+            room_alias (RoomAlias): The alias to look up.
+        Returns:
+            A tuple of:
+                The room ID as a RoomID object.
+                Hosts likely to be participating in the room ([str]).
+        Raises:
+            SynapseError if room alias could not be found.
+        """
+        directory_handler = self.hs.get_handlers().directory_handler
+        mapping = yield directory_handler.get_association(room_alias)
+
+        if not mapping:
+            raise SynapseError(404, "No such room alias")
+
+        room_id = mapping["room_id"]
+        servers = mapping["servers"]
+
+        defer.returnValue((RoomID.from_string(room_id), servers))
+
+    @defer.inlineCallbacks
+    def get_inviter(self, user_id, room_id):
+        invite = yield self.store.get_invite_for_user_in_room(
+            user_id=user_id,
+            room_id=room_id,
+        )
+        if invite:
+            defer.returnValue(UserID.from_string(invite.sender))
+
+    @defer.inlineCallbacks
+    def get_joined_rooms_for_user(self, user):
+        """Returns a list of roomids that the user has any of the given
+        membership states in."""
+
+        rooms = yield self.store.get_rooms_for_user(
+            user.to_string(),
+        )
+
+        # For some reason the list of events contains duplicates
+        # TODO(paul): work out why because I really don't think it should
+        room_ids = set(r.room_id for r in rooms)
+
+        defer.returnValue(room_ids)
+
+    @defer.inlineCallbacks
+    def do_3pid_invite(
+            self,
+            room_id,
+            inviter,
+            medium,
+            address,
+            id_server,
+            requester,
+            txn_id
+    ):
+        invitee = yield self._lookup_3pid(
+            id_server, medium, address
+        )
+
+        if invitee:
+            handler = self.hs.get_handlers().room_member_handler
+            yield handler.update_membership(
+                requester,
+                UserID.from_string(invitee),
+                room_id,
+                "invite",
+                txn_id=txn_id,
+            )
+        else:
+            yield self._make_and_store_3pid_invite(
+                requester,
+                id_server,
+                medium,
+                address,
+                room_id,
+                inviter,
+                txn_id=txn_id
+            )
+
+    @defer.inlineCallbacks
+    def _lookup_3pid(self, id_server, medium, address):
+        """Looks up a 3pid in the passed identity server.
+
+        Args:
+            id_server (str): The server name (including port, if required)
+                of the identity server to use.
+            medium (str): The type of the third party identifier (e.g. "email").
+            address (str): The third party identifier (e.g. "foo@example.com").
+
+        Returns:
+            str: the matrix ID of the 3pid, or None if it is not recognized.
+        """
+        try:
+            data = yield self.hs.get_simple_http_client().get_json(
+                "%s%s/_matrix/identity/api/v1/lookup" % (id_server_scheme, id_server,),
+                {
+                    "medium": medium,
+                    "address": address,
+                }
+            )
+
+            if "mxid" in data:
+                if "signatures" not in data:
+                    raise AuthError(401, "No signatures on 3pid binding")
+                self.verify_any_signature(data, id_server)
+                defer.returnValue(data["mxid"])
+
+        except IOError as e:
+            logger.warn("Error from identity server lookup: %s" % (e,))
+            defer.returnValue(None)
+
+    @defer.inlineCallbacks
+    def verify_any_signature(self, data, server_hostname):
+        if server_hostname not in data["signatures"]:
+            raise AuthError(401, "No signature from server %s" % (server_hostname,))
+        for key_name, signature in data["signatures"][server_hostname].items():
+            key_data = yield self.hs.get_simple_http_client().get_json(
+                "%s%s/_matrix/identity/api/v1/pubkey/%s" %
+                (id_server_scheme, server_hostname, key_name,),
+            )
+            if "public_key" not in key_data:
+                raise AuthError(401, "No public key named %s from %s" %
+                                (key_name, server_hostname,))
+            verify_signed_json(
+                data,
+                server_hostname,
+                decode_verify_key_bytes(key_name, decode_base64(key_data["public_key"]))
+            )
+            return
+
+    @defer.inlineCallbacks
+    def _make_and_store_3pid_invite(
+            self,
+            requester,
+            id_server,
+            medium,
+            address,
+            room_id,
+            user,
+            txn_id
+    ):
+        room_state = yield self.hs.get_state_handler().get_current_state(room_id)
+
+        inviter_display_name = ""
+        inviter_avatar_url = ""
+        member_event = room_state.get((EventTypes.Member, user.to_string()))
+        if member_event:
+            inviter_display_name = member_event.content.get("displayname", "")
+            inviter_avatar_url = member_event.content.get("avatar_url", "")
+
+        canonical_room_alias = ""
+        canonical_alias_event = room_state.get((EventTypes.CanonicalAlias, ""))
+        if canonical_alias_event:
+            canonical_room_alias = canonical_alias_event.content.get("alias", "")
+
+        room_name = ""
+        room_name_event = room_state.get((EventTypes.Name, ""))
+        if room_name_event:
+            room_name = room_name_event.content.get("name", "")
+
+        room_join_rules = ""
+        join_rules_event = room_state.get((EventTypes.JoinRules, ""))
+        if join_rules_event:
+            room_join_rules = join_rules_event.content.get("join_rule", "")
+
+        room_avatar_url = ""
+        room_avatar_event = room_state.get((EventTypes.RoomAvatar, ""))
+        if room_avatar_event:
+            room_avatar_url = room_avatar_event.content.get("url", "")
+
+        token, public_keys, fallback_public_key, display_name = (
+            yield self._ask_id_server_for_third_party_invite(
+                id_server=id_server,
+                medium=medium,
+                address=address,
+                room_id=room_id,
+                inviter_user_id=user.to_string(),
+                room_alias=canonical_room_alias,
+                room_avatar_url=room_avatar_url,
+                room_join_rules=room_join_rules,
+                room_name=room_name,
+                inviter_display_name=inviter_display_name,
+                inviter_avatar_url=inviter_avatar_url
+            )
+        )
+
+        msg_handler = self.hs.get_handlers().message_handler
+        yield msg_handler.create_and_send_nonmember_event(
+            requester,
+            {
+                "type": EventTypes.ThirdPartyInvite,
+                "content": {
+                    "display_name": display_name,
+                    "public_keys": public_keys,
+
+                    # For backwards compatibility:
+                    "key_validity_url": fallback_public_key["key_validity_url"],
+                    "public_key": fallback_public_key["public_key"],
+                },
+                "room_id": room_id,
+                "sender": user.to_string(),
+                "state_key": token,
+            },
+            txn_id=txn_id,
+        )
+
+    @defer.inlineCallbacks
+    def _ask_id_server_for_third_party_invite(
+            self,
+            id_server,
+            medium,
+            address,
+            room_id,
+            inviter_user_id,
+            room_alias,
+            room_avatar_url,
+            room_join_rules,
+            room_name,
+            inviter_display_name,
+            inviter_avatar_url
+    ):
+        """
+        Asks an identity server for a third party invite.
+
+        Args:
+            id_server (str): hostname + optional port for the identity server.
+            medium (str): The literal string "email".
+            address (str): The third party address being invited.
+            room_id (str): The ID of the room to which the user is invited.
+            inviter_user_id (str): The user ID of the inviter.
+            room_alias (str): An alias for the room, for cosmetic notifications.
+            room_avatar_url (str): The URL of the room's avatar, for cosmetic
+                notifications.
+            room_join_rules (str): The join rules of the email (e.g. "public").
+            room_name (str): The m.room.name of the room.
+            inviter_display_name (str): The current display name of the
+                inviter.
+            inviter_avatar_url (str): The URL of the inviter's avatar.
+
+        Returns:
+            A deferred tuple containing:
+                token (str): The token which must be signed to prove authenticity.
+                public_keys ([{"public_key": str, "key_validity_url": str}]):
+                    public_key is a base64-encoded ed25519 public key.
+                fallback_public_key: One element from public_keys.
+                display_name (str): A user-friendly name to represent the invited
+                    user.
+        """
+
+        is_url = "%s%s/_matrix/identity/api/v1/store-invite" % (
+            id_server_scheme, id_server,
+        )
+
+        invite_config = {
+            "medium": medium,
+            "address": address,
+            "room_id": room_id,
+            "room_alias": room_alias,
+            "room_avatar_url": room_avatar_url,
+            "room_join_rules": room_join_rules,
+            "room_name": room_name,
+            "sender": inviter_user_id,
+            "sender_display_name": inviter_display_name,
+            "sender_avatar_url": inviter_avatar_url,
+        }
+
+        if self.hs.config.invite_3pid_guest:
+            registration_handler = self.hs.get_handlers().registration_handler
+            guest_access_token = yield registration_handler.guest_access_token_for(
+                medium=medium,
+                address=address,
+                inviter_user_id=inviter_user_id,
+            )
+
+            guest_user_info = yield self.hs.get_auth().get_user_by_access_token(
+                guest_access_token
+            )
+
+            invite_config.update({
+                "guest_access_token": guest_access_token,
+                "guest_user_id": guest_user_info["user"].to_string(),
+            })
+
+        data = yield self.hs.get_simple_http_client().post_urlencoded_get_json(
+            is_url,
+            invite_config
+        )
+        # TODO: Check for success
+        token = data["token"]
+        public_keys = data.get("public_keys", [])
+        if "public_key" in data:
+            fallback_public_key = {
+                "public_key": data["public_key"],
+                "key_validity_url": "%s%s/_matrix/identity/api/v1/pubkey/isvalid" % (
+                    id_server_scheme, id_server,
+                ),
+            }
+        else:
+            fallback_public_key = public_keys[0]
+
+        if not public_keys:
+            public_keys.append(fallback_public_key)
+        display_name = data["display_name"]
+        defer.returnValue((token, public_keys, fallback_public_key, display_name))
+
+    @defer.inlineCallbacks
+    def forget(self, user, room_id):
+        user_id = user.to_string()
+
+        member = yield self.state_handler.get_current_state(
+            room_id=room_id,
+            event_type=EventTypes.Member,
+            state_key=user_id
+        )
+        membership = member.membership if member else None
+
+        if membership is not None and membership != Membership.LEAVE:
+            raise SynapseError(400, "User %s in room %s" % (
+                user_id, room_id
+            ))
+
+        if membership:
+            yield self.store.forget(user_id, room_id)
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index 48ab5707e1..231140b655 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -17,8 +17,8 @@ from ._base import BaseHandler
 
 from synapse.streams.config import PaginationConfig
 from synapse.api.constants import Membership, EventTypes
-from synapse.util import unwrapFirstError
-from synapse.util.logcontext import LoggingContext, preserve_fn
+from synapse.util.async import concurrently_execute
+from synapse.util.logcontext import LoggingContext
 from synapse.util.metrics import Measure
 from synapse.util.caches.response_cache import ResponseCache
 from synapse.push.clientformat import format_push_rules_for_user
@@ -250,58 +250,50 @@ class SyncHandler(BaseHandler):
         joined = []
         invited = []
         archived = []
-        deferreds = []
-
-        room_list_chunks = [room_list[i:i + 10] for i in xrange(0, len(room_list), 10)]
-        for room_list_chunk in room_list_chunks:
-            for event in room_list_chunk:
-                if event.membership == Membership.JOIN:
-                    room_sync_deferred = preserve_fn(
-                        self.full_state_sync_for_joined_room
-                    )(
-                        room_id=event.room_id,
-                        sync_config=sync_config,
-                        now_token=now_token,
-                        timeline_since_token=timeline_since_token,
-                        ephemeral_by_room=ephemeral_by_room,
-                        tags_by_room=tags_by_room,
-                        account_data_by_room=account_data_by_room,
-                    )
-                    room_sync_deferred.addCallback(joined.append)
-                    deferreds.append(room_sync_deferred)
-                elif event.membership == Membership.INVITE:
-                    invite = yield self.store.get_event(event.event_id)
-                    invited.append(InvitedSyncResult(
-                        room_id=event.room_id,
-                        invite=invite,
-                    ))
-                elif event.membership in (Membership.LEAVE, Membership.BAN):
-                    # Always send down rooms we were banned or kicked from.
-                    if not sync_config.filter_collection.include_leave:
-                        if event.membership == Membership.LEAVE:
-                            if sync_config.user.to_string() == event.sender:
-                                continue
-
-                    leave_token = now_token.copy_and_replace(
-                        "room_key", "s%d" % (event.stream_ordering,)
-                    )
-                    room_sync_deferred = preserve_fn(
-                        self.full_state_sync_for_archived_room
-                    )(
-                        sync_config=sync_config,
-                        room_id=event.room_id,
-                        leave_event_id=event.event_id,
-                        leave_token=leave_token,
-                        timeline_since_token=timeline_since_token,
-                        tags_by_room=tags_by_room,
-                        account_data_by_room=account_data_by_room,
-                    )
-                    room_sync_deferred.addCallback(archived.append)
-                    deferreds.append(room_sync_deferred)
 
-            yield defer.gatherResults(
-                deferreds, consumeErrors=True
-            ).addErrback(unwrapFirstError)
+        user_id = sync_config.user.to_string()
+
+        @defer.inlineCallbacks
+        def _generate_room_entry(event):
+            if event.membership == Membership.JOIN:
+                room_result = yield self.full_state_sync_for_joined_room(
+                    room_id=event.room_id,
+                    sync_config=sync_config,
+                    now_token=now_token,
+                    timeline_since_token=timeline_since_token,
+                    ephemeral_by_room=ephemeral_by_room,
+                    tags_by_room=tags_by_room,
+                    account_data_by_room=account_data_by_room,
+                )
+                joined.append(room_result)
+            elif event.membership == Membership.INVITE:
+                invite = yield self.store.get_event(event.event_id)
+                invited.append(InvitedSyncResult(
+                    room_id=event.room_id,
+                    invite=invite,
+                ))
+            elif event.membership in (Membership.LEAVE, Membership.BAN):
+                # Always send down rooms we were banned or kicked from.
+                if not sync_config.filter_collection.include_leave:
+                    if event.membership == Membership.LEAVE:
+                        if user_id == event.sender:
+                            return
+
+                leave_token = now_token.copy_and_replace(
+                    "room_key", "s%d" % (event.stream_ordering,)
+                )
+                room_result = yield self.full_state_sync_for_archived_room(
+                    sync_config=sync_config,
+                    room_id=event.room_id,
+                    leave_event_id=event.event_id,
+                    leave_token=leave_token,
+                    timeline_since_token=timeline_since_token,
+                    tags_by_room=tags_by_room,
+                    account_data_by_room=account_data_by_room,
+                )
+                archived.append(room_result)
+
+        yield concurrently_execute(_generate_room_entry, room_list, 10)
 
         account_data_for_user = sync_config.filter_collection.filter_account_data(
             self.account_data_for_user(account_data)
@@ -671,7 +663,8 @@ class SyncHandler(BaseHandler):
     def load_filtered_recents(self, room_id, sync_config, now_token,
                               since_token=None, recents=None, newly_joined_room=False):
         """
-        :returns a Deferred TimelineBatch
+        Returns:
+            a Deferred TimelineBatch
         """
         with Measure(self.clock, "load_filtered_recents"):
             filtering_factor = 2
@@ -838,8 +831,11 @@ class SyncHandler(BaseHandler):
         """
         Get the room state after the given event
 
-        :param synapse.events.EventBase event: event of interest
-        :return: A Deferred map from ((type, state_key)->Event)
+        Args:
+            event(synapse.events.EventBase): event of interest
+
+        Returns:
+            A Deferred map from ((type, state_key)->Event)
         """
         state = yield self.store.get_state_for_event(event.event_id)
         if event.is_state():
@@ -850,9 +846,13 @@ class SyncHandler(BaseHandler):
     @defer.inlineCallbacks
     def get_state_at(self, room_id, stream_position):
         """ Get the room state at a particular stream position
-        :param str room_id: room for which to get state
-        :param StreamToken stream_position: point at which to get state
-        :returns: A Deferred map from ((type, state_key)->Event)
+
+        Args:
+            room_id(str): room for which to get state
+            stream_position(StreamToken): point at which to get state
+
+        Returns:
+            A Deferred map from ((type, state_key)->Event)
         """
         last_events, token = yield self.store.get_recent_events_for_room(
             room_id, end_token=stream_position.room_key, limit=1,
@@ -873,15 +873,18 @@ class SyncHandler(BaseHandler):
         """ Works out the differnce in state between the start of the timeline
         and the previous sync.
 
-        :param str room_id
-        :param TimelineBatch batch: The timeline batch for the room that will
-            be sent to the user.
-        :param sync_config
-        :param str since_token: Token of the end of the previous batch. May be None.
-        :param str now_token: Token of the end of the current batch.
-        :param bool full_state: Whether to force returning the full state.
+        Args:
+            room_id(str):
+            batch(synapse.handlers.sync.TimelineBatch): The timeline batch for
+                the room that will be sent to the user.
+            sync_config(synapse.handlers.sync.SyncConfig):
+            since_token(str|None): Token of the end of the previous batch. May
+                be None.
+            now_token(str): Token of the end of the current batch.
+            full_state(bool): Whether to force returning the full state.
 
-        :returns A new event dictionary
+        Returns:
+             A deferred new event dictionary
         """
         # TODO(mjark) Check if the state events were received by the server
         # after the previous sync, since we need to include those state
@@ -953,11 +956,13 @@ class SyncHandler(BaseHandler):
         Check if the user has just joined the given room (so should
         be given the full state)
 
-        :param sync_config:
-        :param dict[(str,str), synapse.events.FrozenEvent] state_delta: the
-           difference in state since the last sync
+        Args:
+            sync_config(synapse.handlers.sync.SyncConfig):
+            state_delta(dict[(str,str), synapse.events.FrozenEvent]): the
+                difference in state since the last sync
 
-        :returns A deferred Tuple (state_delta, limited)
+        Returns:
+             A deferred Tuple (state_delta, limited)
         """
         join_event = state_delta.get((
             EventTypes.Member, sync_config.user.to_string()), None)
diff --git a/synapse/http/servlet.py b/synapse/http/servlet.py
index 1c8bd8666f..e41afeab8e 100644
--- a/synapse/http/servlet.py
+++ b/synapse/http/servlet.py
@@ -26,14 +26,19 @@ logger = logging.getLogger(__name__)
 def parse_integer(request, name, default=None, required=False):
     """Parse an integer parameter from the request string
 
-    :param request: the twisted HTTP request.
-    :param name (str): the name of the query parameter.
-    :param default: value to use if the parameter is absent, defaults to None.
-    :param required (bool): whether to raise a 400 SynapseError if the
-        parameter is absent, defaults to False.
-    :return: An int value or the default.
-    :raises
-        SynapseError if the parameter is absent and required, or if the
+    Args:
+        request: the twisted HTTP request.
+        name (str): the name of the query parameter.
+        default (int|None): value to use if the parameter is absent, defaults
+            to None.
+        required (bool): whether to raise a 400 SynapseError if the
+            parameter is absent, defaults to False.
+
+    Returns:
+        int|None: An int value or the default.
+
+    Raises:
+        SynapseError: if the parameter is absent and required, or if the
             parameter is present and not an integer.
     """
     if name in request.args:
@@ -53,14 +58,19 @@ def parse_integer(request, name, default=None, required=False):
 def parse_boolean(request, name, default=None, required=False):
     """Parse a boolean parameter from the request query string
 
-    :param request: the twisted HTTP request.
-    :param name (str): the name of the query parameter.
-    :param default: value to use if the parameter is absent, defaults to None.
-    :param required (bool): whether to raise a 400 SynapseError if the
-        parameter is absent, defaults to False.
-    :return: A bool value or the default.
-    :raises
-        SynapseError if the parameter is absent and required, or if the
+    Args:
+        request: the twisted HTTP request.
+        name (str): the name of the query parameter.
+        default (bool|None): value to use if the parameter is absent, defaults
+            to None.
+        required (bool): whether to raise a 400 SynapseError if the
+            parameter is absent, defaults to False.
+
+    Returns:
+        bool|None: A bool value or the default.
+
+    Raises:
+        SynapseError: if the parameter is absent and required, or if the
             parameter is present and not one of "true" or "false".
     """
 
@@ -88,15 +98,20 @@ def parse_string(request, name, default=None, required=False,
                  allowed_values=None, param_type="string"):
     """Parse a string parameter from the request query string.
 
-    :param request: the twisted HTTP request.
-    :param name (str): the name of the query parameter.
-    :param default: value to use if the parameter is absent, defaults to None.
-    :param required (bool): whether to raise a 400 SynapseError if the
-        parameter is absent, defaults to False.
-    :param allowed_values (list): List of allowed values for the string,
-        or None if any value is allowed, defaults to None
-    :return: A string value or the default.
-    :raises
+    Args:
+        request: the twisted HTTP request.
+        name (str): the name of the query parameter.
+        default (str|None): value to use if the parameter is absent, defaults
+            to None.
+        required (bool): whether to raise a 400 SynapseError if the
+            parameter is absent, defaults to False.
+        allowed_values (list[str]): List of allowed values for the string,
+            or None if any value is allowed, defaults to None
+
+    Returns:
+        str|None: A string value or the default.
+
+    Raises:
         SynapseError if the parameter is absent and required, or if the
             parameter is present, must be one of a list of allowed values and
             is not one of those allowed values.
@@ -122,9 +137,13 @@ def parse_string(request, name, default=None, required=False,
 def parse_json_value_from_request(request):
     """Parse a JSON value from the body of a twisted HTTP request.
 
-    :param request: the twisted HTTP request.
-    :returns: The JSON value.
-    :raises
+    Args:
+        request: the twisted HTTP request.
+
+    Returns:
+        The JSON value.
+
+    Raises:
         SynapseError if the request body couldn't be decoded as JSON.
     """
     try:
@@ -143,8 +162,10 @@ def parse_json_value_from_request(request):
 def parse_json_object_from_request(request):
     """Parse a JSON object from the body of a twisted HTTP request.
 
-    :param request: the twisted HTTP request.
-    :raises
+    Args:
+        request: the twisted HTTP request.
+
+    Raises:
         SynapseError if the request body couldn't be decoded as JSON or
             if it wasn't a JSON object.
     """
diff --git a/synapse/notifier.py b/synapse/notifier.py
index f00cd8c588..6af7a8f424 100644
--- a/synapse/notifier.py
+++ b/synapse/notifier.py
@@ -503,13 +503,14 @@ class Notifier(object):
     def wait_for_replication(self, callback, timeout):
         """Wait for an event to happen.
 
-        :param callback:
-            Gets called whenever an event happens. If this returns a truthy
-            value then ``wait_for_replication`` returns, otherwise it waits
-            for another event.
-        :param int timeout:
-            How many milliseconds to wait for callback return a truthy value.
-        :returns:
+        Args:
+            callback: Gets called whenever an event happens. If this returns a
+                truthy value then ``wait_for_replication`` returns, otherwise
+                it waits for another event.
+            timeout: How many milliseconds to wait for callback return a truthy
+                value.
+
+        Returns:
             A deferred that resolves with the value returned by the callback.
         """
         listener = _NotificationListener(None)
diff --git a/synapse/push/baserules.py b/synapse/push/baserules.py
index 792af70eb7..6add94beeb 100644
--- a/synapse/push/baserules.py
+++ b/synapse/push/baserules.py
@@ -19,9 +19,11 @@ import copy
 def list_with_base_rules(rawrules):
     """Combine the list of rules set by the user with the default push rules
 
-    :param list rawrules: The rules the user has modified or set.
-    :returns: A new list with the rules set by the user combined with the
-        defaults.
+    Args:
+        rawrules(list): The rules the user has modified or set.
+
+    Returns:
+        A new list with the rules set by the user combined with the defaults.
     """
     ruleslist = []
 
diff --git a/synapse/push/push_rule_evaluator.py b/synapse/push/push_rule_evaluator.py
index 51f73a5b78..c3c2877629 100644
--- a/synapse/push/push_rule_evaluator.py
+++ b/synapse/push/push_rule_evaluator.py
@@ -133,8 +133,9 @@ class PushRuleEvaluator:
             enabled = self.enabled_map.get(r['rule_id'], None)
             if enabled is not None and not enabled:
                 continue
-
-            if not r.get("enabled", True):
+            elif enabled is None and not r.get("enabled", True):
+                # if no override, check enabled on the rule itself
+                # (may have come from a base rule)
                 continue
 
             conditions = r['conditions']
diff --git a/synapse/replication/resource.py b/synapse/replication/resource.py
index 33cb2eafa3..a543af68f8 100644
--- a/synapse/replication/resource.py
+++ b/synapse/replication/resource.py
@@ -145,32 +145,43 @@ class ReplicationResource(Resource):
         timeout = parse_integer(request, "timeout", 10 * 1000)
 
         request.setHeader(b"Content-Type", b"application/json")
-        writer = _Writer(request)
 
-        @defer.inlineCallbacks
-        def replicate():
-            current_token = yield self.current_replication_token()
-            logger.info("Replicating up to %r", current_token)
-
-            yield self.account_data(writer, current_token, limit)
-            yield self.events(writer, current_token, limit)
-            yield self.presence(writer, current_token)  # TODO: implement limit
-            yield self.typing(writer, current_token)  # TODO: implement limit
-            yield self.receipts(writer, current_token, limit)
-            yield self.push_rules(writer, current_token, limit)
-            yield self.pushers(writer, current_token, limit)
-            yield self.state(writer, current_token, limit)
-            self.streams(writer, current_token)
+        request_streams = {
+            name: parse_integer(request, name)
+            for names in STREAM_NAMES for name in names
+        }
+        request_streams["streams"] = parse_string(request, "streams")
 
-            logger.info("Replicated %d rows", writer.total)
-            defer.returnValue(writer.total)
+        def replicate():
+            return self.replicate(request_streams, limit)
 
-        yield self.notifier.wait_for_replication(replicate, timeout)
+        result = yield self.notifier.wait_for_replication(replicate, timeout)
 
-        writer.finish()
+        request.write(json.dumps(result, ensure_ascii=False))
+        finish_request(request)
 
-    def streams(self, writer, current_token):
-        request_token = parse_string(writer.request, "streams")
+    @defer.inlineCallbacks
+    def replicate(self, request_streams, limit):
+        writer = _Writer()
+        current_token = yield self.current_replication_token()
+        logger.info("Replicating up to %r", current_token)
+
+        yield self.account_data(writer, current_token, limit, request_streams)
+        yield self.events(writer, current_token, limit, request_streams)
+        # TODO: implement limit
+        yield self.presence(writer, current_token, request_streams)
+        yield self.typing(writer, current_token, request_streams)
+        yield self.receipts(writer, current_token, limit, request_streams)
+        yield self.push_rules(writer, current_token, limit, request_streams)
+        yield self.pushers(writer, current_token, limit, request_streams)
+        yield self.state(writer, current_token, limit, request_streams)
+        self.streams(writer, current_token, request_streams)
+
+        logger.info("Replicated %d rows", writer.total)
+        defer.returnValue(writer.finish())
+
+    def streams(self, writer, current_token, request_streams):
+        request_token = request_streams.get("streams")
 
         streams = []
 
@@ -195,32 +206,43 @@ class ReplicationResource(Resource):
                 )
 
     @defer.inlineCallbacks
-    def events(self, writer, current_token, limit):
-        request_events = parse_integer(writer.request, "events")
-        request_backfill = parse_integer(writer.request, "backfill")
+    def events(self, writer, current_token, limit, request_streams):
+        request_events = request_streams.get("events")
+        request_backfill = request_streams.get("backfill")
 
         if request_events is not None or request_backfill is not None:
             if request_events is None:
                 request_events = current_token.events
             if request_backfill is None:
                 request_backfill = current_token.backfill
-            events_rows, backfill_rows = yield self.store.get_all_new_events(
+            res = yield self.store.get_all_new_events(
                 request_backfill, request_events,
                 current_token.backfill, current_token.events,
                 limit
             )
-            writer.write_header_and_rows("events", events_rows, (
+            writer.write_header_and_rows("events", res.new_forward_events, (
                 "position", "internal", "json", "state_group"
             ))
-            writer.write_header_and_rows("backfill", backfill_rows, (
+            writer.write_header_and_rows("backfill", res.new_backfill_events, (
                 "position", "internal", "json", "state_group"
             ))
+            writer.write_header_and_rows(
+                "forward_ex_outliers", res.forward_ex_outliers,
+                ("position", "event_id", "state_group")
+            )
+            writer.write_header_and_rows(
+                "backward_ex_outliers", res.backward_ex_outliers,
+                ("position", "event_id", "state_group")
+            )
+            writer.write_header_and_rows(
+                "state_resets", res.state_resets, ("position",)
+            )
 
     @defer.inlineCallbacks
-    def presence(self, writer, current_token):
+    def presence(self, writer, current_token, request_streams):
         current_position = current_token.presence
 
-        request_presence = parse_integer(writer.request, "presence")
+        request_presence = request_streams.get("presence")
 
         if request_presence is not None:
             presence_rows = yield self.presence_handler.get_all_presence_updates(
@@ -233,10 +255,10 @@ class ReplicationResource(Resource):
             ))
 
     @defer.inlineCallbacks
-    def typing(self, writer, current_token):
+    def typing(self, writer, current_token, request_streams):
         current_position = current_token.presence
 
-        request_typing = parse_integer(writer.request, "typing")
+        request_typing = request_streams.get("typing")
 
         if request_typing is not None:
             typing_rows = yield self.typing_handler.get_all_typing_updates(
@@ -247,10 +269,10 @@ class ReplicationResource(Resource):
             ))
 
     @defer.inlineCallbacks
-    def receipts(self, writer, current_token, limit):
+    def receipts(self, writer, current_token, limit, request_streams):
         current_position = current_token.receipts
 
-        request_receipts = parse_integer(writer.request, "receipts")
+        request_receipts = request_streams.get("receipts")
 
         if request_receipts is not None:
             receipts_rows = yield self.store.get_all_updated_receipts(
@@ -261,12 +283,12 @@ class ReplicationResource(Resource):
             ))
 
     @defer.inlineCallbacks
-    def account_data(self, writer, current_token, limit):
+    def account_data(self, writer, current_token, limit, request_streams):
         current_position = current_token.account_data
 
-        user_account_data = parse_integer(writer.request, "user_account_data")
-        room_account_data = parse_integer(writer.request, "room_account_data")
-        tag_account_data = parse_integer(writer.request, "tag_account_data")
+        user_account_data = request_streams.get("user_account_data")
+        room_account_data = request_streams.get("room_account_data")
+        tag_account_data = request_streams.get("tag_account_data")
 
         if user_account_data is not None or room_account_data is not None:
             if user_account_data is None:
@@ -292,10 +314,10 @@ class ReplicationResource(Resource):
             ))
 
     @defer.inlineCallbacks
-    def push_rules(self, writer, current_token, limit):
+    def push_rules(self, writer, current_token, limit, request_streams):
         current_position = current_token.push_rules
 
-        push_rules = parse_integer(writer.request, "push_rules")
+        push_rules = request_streams.get("push_rules")
 
         if push_rules is not None:
             rows = yield self.store.get_all_push_rule_updates(
@@ -307,10 +329,11 @@ class ReplicationResource(Resource):
             ))
 
     @defer.inlineCallbacks
-    def pushers(self, writer, current_token, limit):
+    def pushers(self, writer, current_token, limit, request_streams):
         current_position = current_token.pushers
 
-        pushers = parse_integer(writer.request, "pushers")
+        pushers = request_streams.get("pushers")
+
         if pushers is not None:
             updated, deleted = yield self.store.get_all_updated_pushers(
                 pushers, current_position, limit
@@ -325,10 +348,11 @@ class ReplicationResource(Resource):
             ))
 
     @defer.inlineCallbacks
-    def state(self, writer, current_token, limit):
+    def state(self, writer, current_token, limit, request_streams):
         current_position = current_token.state
 
-        state = parse_integer(writer.request, "state")
+        state = request_streams.get("state")
+
         if state is not None:
             state_groups, state_group_state = (
                 yield self.store.get_all_new_state_groups(
@@ -345,9 +369,8 @@ class ReplicationResource(Resource):
 
 class _Writer(object):
     """Writes the streams as a JSON object as the response to the request"""
-    def __init__(self, request):
+    def __init__(self):
         self.streams = {}
-        self.request = request
         self.total = 0
 
     def write_header_and_rows(self, name, rows, fields, position=None):
@@ -366,8 +389,7 @@ class _Writer(object):
         self.total += len(rows)
 
     def finish(self):
-        self.request.write(json.dumps(self.streams, ensure_ascii=False))
-        finish_request(self.request)
+        return self.streams
 
 
 class _ReplicationToken(collections.namedtuple("_ReplicationToken", (
diff --git a/synapse/replication/slave/__init__.py b/synapse/replication/slave/__init__.py
new file mode 100644
index 0000000000..b7df13c9ee
--- /dev/null
+++ b/synapse/replication/slave/__init__.py
@@ -0,0 +1,14 @@
+# -*- coding: utf-8 -*-
+# Copyright 2016 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
diff --git a/synapse/replication/slave/storage/__init__.py b/synapse/replication/slave/storage/__init__.py
new file mode 100644
index 0000000000..b7df13c9ee
--- /dev/null
+++ b/synapse/replication/slave/storage/__init__.py
@@ -0,0 +1,14 @@
+# -*- coding: utf-8 -*-
+# Copyright 2016 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
diff --git a/synapse/replication/slave/storage/_base.py b/synapse/replication/slave/storage/_base.py
new file mode 100644
index 0000000000..46e43ce1c7
--- /dev/null
+++ b/synapse/replication/slave/storage/_base.py
@@ -0,0 +1,28 @@
+# -*- coding: utf-8 -*-
+# Copyright 2016 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from synapse.storage._base import SQLBaseStore
+from twisted.internet import defer
+
+
+class BaseSlavedStore(SQLBaseStore):
+    def __init__(self, db_conn, hs):
+        super(BaseSlavedStore, self).__init__(hs)
+
+    def stream_positions(self):
+        return {}
+
+    def process_replication(self, result):
+        return defer.succeed(None)
diff --git a/synapse/replication/slave/storage/_slaved_id_tracker.py b/synapse/replication/slave/storage/_slaved_id_tracker.py
new file mode 100644
index 0000000000..24b5c79d4a
--- /dev/null
+++ b/synapse/replication/slave/storage/_slaved_id_tracker.py
@@ -0,0 +1,30 @@
+# -*- coding: utf-8 -*-
+# Copyright 2016 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from synapse.storage.util.id_generators import _load_current_id
+
+
+class SlavedIdTracker(object):
+    def __init__(self, db_conn, table, column, extra_tables=[], step=1):
+        self.step = step
+        self._current = _load_current_id(db_conn, table, column, step)
+        for table, column in extra_tables:
+            self.advance(_load_current_id(db_conn, table, column))
+
+    def advance(self, new_id):
+        self._current = (max if self.step > 0 else min)(self._current, new_id)
+
+    def get_current_token(self):
+        return self._current
diff --git a/synapse/replication/slave/storage/events.py b/synapse/replication/slave/storage/events.py
new file mode 100644
index 0000000000..680dc89536
--- /dev/null
+++ b/synapse/replication/slave/storage/events.py
@@ -0,0 +1,199 @@
+# -*- coding: utf-8 -*-
+# Copyright 2016 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from ._base import BaseSlavedStore
+from ._slaved_id_tracker import SlavedIdTracker
+
+from synapse.api.constants import EventTypes
+from synapse.events import FrozenEvent
+from synapse.storage import DataStore
+from synapse.storage.room import RoomStore
+from synapse.storage.roommember import RoomMemberStore
+from synapse.storage.event_federation import EventFederationStore
+from synapse.storage.state import StateStore
+from synapse.util.caches.stream_change_cache import StreamChangeCache
+
+import ujson as json
+
+# So, um, we want to borrow a load of functions intended for reading from
+# a DataStore, but we don't want to take functions that either write to the
+# DataStore or are cached and don't have cache invalidation logic.
+#
+# Rather than write duplicate versions of those functions, or lift them to
+# a common base class, we going to grab the underlying __func__ object from
+# the method descriptor on the DataStore and chuck them into our class.
+
+
+class SlavedEventStore(BaseSlavedStore):
+
+    def __init__(self, db_conn, hs):
+        super(SlavedEventStore, self).__init__(db_conn, hs)
+        self._stream_id_gen = SlavedIdTracker(
+            db_conn, "events", "stream_ordering",
+        )
+        self._backfill_id_gen = SlavedIdTracker(
+            db_conn, "events", "stream_ordering", step=-1
+        )
+        events_max = self._stream_id_gen.get_current_token()
+        event_cache_prefill, min_event_val = self._get_cache_dict(
+            db_conn, "events",
+            entity_column="room_id",
+            stream_column="stream_ordering",
+            max_value=events_max,
+        )
+        self._events_stream_cache = StreamChangeCache(
+            "EventsRoomStreamChangeCache", min_event_val,
+            prefilled_cache=event_cache_prefill,
+        )
+
+    # Cached functions can't be accessed through a class instance so we need
+    # to reach inside the __dict__ to extract them.
+    get_room_name_and_aliases = RoomStore.__dict__["get_room_name_and_aliases"]
+    get_rooms_for_user = RoomMemberStore.__dict__["get_rooms_for_user"]
+    get_users_in_room = RoomMemberStore.__dict__["get_users_in_room"]
+    get_latest_event_ids_in_room = EventFederationStore.__dict__[
+        "get_latest_event_ids_in_room"
+    ]
+    _get_current_state_for_key = StateStore.__dict__[
+        "_get_current_state_for_key"
+    ]
+
+    get_current_state = DataStore.get_current_state.__func__
+    get_current_state_for_key = DataStore.get_current_state_for_key.__func__
+    get_rooms_for_user_where_membership_is = (
+        DataStore.get_rooms_for_user_where_membership_is.__func__
+    )
+    get_membership_changes_for_user = (
+        DataStore.get_membership_changes_for_user.__func__
+    )
+    get_room_events_max_id = DataStore.get_room_events_max_id.__func__
+    get_room_events_stream_for_room = (
+        DataStore.get_room_events_stream_for_room.__func__
+    )
+    _set_before_and_after = DataStore._set_before_and_after
+
+    _get_events = DataStore._get_events.__func__
+    _get_events_from_cache = DataStore._get_events_from_cache.__func__
+
+    _invalidate_get_event_cache = DataStore._invalidate_get_event_cache.__func__
+    _parse_events_txn = DataStore._parse_events_txn.__func__
+    _get_events_txn = DataStore._get_events_txn.__func__
+    _fetch_events_txn = DataStore._fetch_events_txn.__func__
+    _fetch_event_rows = DataStore._fetch_event_rows.__func__
+    _get_event_from_row_txn = DataStore._get_event_from_row_txn.__func__
+    _get_rooms_for_user_where_membership_is_txn = (
+        DataStore._get_rooms_for_user_where_membership_is_txn.__func__
+    )
+    _get_members_rows_txn = DataStore._get_members_rows_txn.__func__
+
+    def stream_positions(self):
+        result = super(SlavedEventStore, self).stream_positions()
+        result["events"] = self._stream_id_gen.get_current_token()
+        result["backfilled"] = self._backfill_id_gen.get_current_token()
+        return result
+
+    def process_replication(self, result):
+        state_resets = set(
+            r[0] for r in result.get("state_resets", {"rows": []})["rows"]
+        )
+
+        stream = result.get("events")
+        if stream:
+            self._stream_id_gen.advance(stream["position"])
+            for row in stream["rows"]:
+                self._process_replication_row(
+                    row, backfilled=False, state_resets=state_resets
+                )
+
+        stream = result.get("backfill")
+        if stream:
+            self._backfill_id_gen.advance(stream["position"])
+            for row in stream["rows"]:
+                self._process_replication_row(
+                    row, backfilled=True, state_resets=state_resets
+                )
+
+        stream = result.get("forward_ex_outliers")
+        if stream:
+            for row in stream["rows"]:
+                event_id = row[1]
+                self._invalidate_get_event_cache(event_id)
+
+        stream = result.get("backward_ex_outliers")
+        if stream:
+            for row in stream["rows"]:
+                event_id = row[1]
+                self._invalidate_get_event_cache(event_id)
+
+        return super(SlavedEventStore, self).process_replication(result)
+
+    def _process_replication_row(self, row, backfilled, state_resets):
+        position = row[0]
+        internal = json.loads(row[1])
+        event_json = json.loads(row[2])
+
+        event = FrozenEvent(event_json, internal_metadata_dict=internal)
+        self._invalidate_caches_for_event(
+            event, backfilled, reset_state=position in state_resets
+        )
+
+    def _invalidate_caches_for_event(self, event, backfilled, reset_state):
+        if reset_state:
+            self._get_current_state_for_key.invalidate_all()
+            self.get_rooms_for_user.invalidate_all()
+            self.get_users_in_room.invalidate((event.room_id,))
+            # self.get_joined_hosts_for_room.invalidate((event.room_id,))
+            self.get_room_name_and_aliases.invalidate((event.room_id,))
+
+        self._invalidate_get_event_cache(event.event_id)
+
+        if not backfilled:
+            self._events_stream_cache.entity_has_changed(
+                event.room_id, event.internal_metadata.stream_ordering
+            )
+
+        # self.get_unread_event_push_actions_by_room_for_user.invalidate_many(
+        #     (event.room_id,)
+        # )
+
+        if event.type == EventTypes.Redaction:
+            self._invalidate_get_event_cache(event.redacts)
+
+        if event.type == EventTypes.Member:
+            self.get_rooms_for_user.invalidate((event.state_key,))
+            # self.get_joined_hosts_for_room.invalidate((event.room_id,))
+            self.get_users_in_room.invalidate((event.room_id,))
+            # self._membership_stream_cache.entity_has_changed(
+            #    event.state_key, event.internal_metadata.stream_ordering
+            # )
+
+        if not event.is_state():
+            return
+
+        if backfilled:
+            return
+
+        if (not event.internal_metadata.is_invite_from_remote()
+                and event.internal_metadata.is_outlier()):
+            return
+
+        self._get_current_state_for_key.invalidate((
+            event.room_id, event.type, event.state_key
+        ))
+
+        if event.type in [EventTypes.Name, EventTypes.Aliases]:
+            self.get_room_name_and_aliases.invalidate(
+                (event.room_id,)
+            )
+            pass
diff --git a/synapse/rest/client/v2_alpha/sync.py b/synapse/rest/client/v2_alpha/sync.py
index c5785d7074..60d3dc4030 100644
--- a/synapse/rest/client/v2_alpha/sync.py
+++ b/synapse/rest/client/v2_alpha/sync.py
@@ -199,15 +199,17 @@ class SyncRestServlet(RestServlet):
         """
         Encode the joined rooms in a sync result
 
-        :param list[synapse.handlers.sync.JoinedSyncResult] rooms: list of sync
-            results for rooms this user is joined to
-        :param int time_now: current time - used as a baseline for age
-            calculations
-        :param int token_id: ID of the user's auth token - used for namespacing
-            of transaction IDs
-
-        :return: the joined rooms list, in our response format
-        :rtype: dict[str, dict[str, object]]
+        Args:
+            rooms(list[synapse.handlers.sync.JoinedSyncResult]): list of sync
+                results for rooms this user is joined to
+            time_now(int): current time - used as a baseline for age
+                calculations
+            token_id(int): ID of the user's auth token - used for namespacing
+                of transaction IDs
+
+        Returns:
+            dict[str, dict[str, object]]: the joined rooms list, in our
+                response format
         """
         joined = {}
         for room in rooms:
@@ -221,15 +223,17 @@ class SyncRestServlet(RestServlet):
         """
         Encode the invited rooms in a sync result
 
-        :param list[synapse.handlers.sync.InvitedSyncResult] rooms: list of
-             sync results for rooms this user is joined to
-        :param int time_now: current time - used as a baseline for age
-            calculations
-        :param int token_id: ID of the user's auth token - used for namespacing
+        Args:
+            rooms(list[synapse.handlers.sync.InvitedSyncResult]): list of
+                sync results for rooms this user is joined to
+            time_now(int): current time - used as a baseline for age
+                calculations
+            token_id(int): ID of the user's auth token - used for namespacing
             of transaction IDs
 
-        :return: the invited rooms list, in our response format
-        :rtype: dict[str, dict[str, object]]
+        Returns:
+            dict[str, dict[str, object]]: the invited rooms list, in our
+                response format
         """
         invited = {}
         for room in rooms:
@@ -251,15 +255,17 @@ class SyncRestServlet(RestServlet):
         """
         Encode the archived rooms in a sync result
 
-        :param list[synapse.handlers.sync.ArchivedSyncResult] rooms: list of
-             sync results for rooms this user is joined to
-        :param int time_now: current time - used as a baseline for age
-            calculations
-        :param int token_id: ID of the user's auth token - used for namespacing
-            of transaction IDs
-
-        :return: the invited rooms list, in our response format
-        :rtype: dict[str, dict[str, object]]
+        Args:
+            rooms (list[synapse.handlers.sync.ArchivedSyncResult]): list of
+                sync results for rooms this user is joined to
+            time_now(int): current time - used as a baseline for age
+                calculations
+            token_id(int): ID of the user's auth token - used for namespacing
+                of transaction IDs
+
+        Returns:
+            dict[str, dict[str, object]]: The invited rooms list, in our
+                response format
         """
         joined = {}
         for room in rooms:
@@ -272,17 +278,18 @@ class SyncRestServlet(RestServlet):
     @staticmethod
     def encode_room(room, time_now, token_id, joined=True):
         """
-        :param JoinedSyncResult|ArchivedSyncResult room: sync result for a
-            single room
-        :param int time_now: current time - used as a baseline for age
-            calculations
-        :param int token_id: ID of the user's auth token - used for namespacing
-            of transaction IDs
-        :param joined: True if the user is joined to this room - will mean
-            we handle ephemeral events
-
-        :return: the room, encoded in our response format
-        :rtype: dict[str, object]
+        Args:
+            room (JoinedSyncResult|ArchivedSyncResult): sync result for a
+                single room
+            time_now (int): current time - used as a baseline for age
+                calculations
+            token_id (int): ID of the user's auth token - used for namespacing
+                of transaction IDs
+            joined (bool): True if the user is joined to this room - will mean
+                we handle ephemeral events
+
+        Returns:
+            dict[str, object]: the room, encoded in our response format
         """
         def serialize(event):
             # TODO(mjark): Respect formatting requirements in the filter.
diff --git a/synapse/state.py b/synapse/state.py
index 41d32e664a..58211f5feb 100644
--- a/synapse/state.py
+++ b/synapse/state.py
@@ -75,7 +75,8 @@ class StateHandler(object):
         self._state_cache.start()
 
     @defer.inlineCallbacks
-    def get_current_state(self, room_id, event_type=None, state_key=""):
+    def get_current_state(self, room_id, event_type=None, state_key="",
+                          latest_event_ids=None):
         """ Retrieves the current state for the room. This is done by
         calling `get_latest_events_in_room` to get the leading edges of the
         event graph and then resolving any of the state conflicts.
@@ -86,11 +87,13 @@ class StateHandler(object):
         If `event_type` is specified, then the method returns only the one
         event (or None) with that `event_type` and `state_key`.
 
-        :returns map from (type, state_key) to event
+        Returns:
+            map from (type, state_key) to event
         """
-        event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
+        if not latest_event_ids:
+            latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
 
-        res = yield self.resolve_state_groups(room_id, event_ids)
+        res = yield self.resolve_state_groups(room_id, latest_event_ids)
         state = res[1]
 
         if event_type:
@@ -100,7 +103,7 @@ class StateHandler(object):
         defer.returnValue(state)
 
     @defer.inlineCallbacks
-    def compute_event_context(self, event, old_state=None, outlier=False):
+    def compute_event_context(self, event, old_state=None):
         """ Fills out the context with the `current state` of the graph. The
         `current state` here is defined to be the state of the event graph
         just before the event - i.e. it never includes `event`
@@ -115,7 +118,7 @@ class StateHandler(object):
         """
         context = EventContext()
 
-        if outlier:
+        if event.internal_metadata.is_outlier():
             # If this is an outlier, then we know it shouldn't have any current
             # state. Certainly store.get_current_state won't return any, and
             # persisting the event won't store the state group.
@@ -176,10 +179,11 @@ class StateHandler(object):
         """ Given a list of event_ids this method fetches the state at each
         event, resolves conflicts between them and returns them.
 
-        :returns a Deferred tuple of (`state_group`, `state`, `prev_state`).
-        `state_group` is the name of a state group if one and only one is
-        involved. `state` is a map from (type, state_key) to event, and
-        `prev_state` is a list of event ids.
+        Returns:
+            a Deferred tuple of (`state_group`, `state`, `prev_state`).
+            `state_group` is the name of a state group if one and only one is
+            involved. `state` is a map from (type, state_key) to event, and
+            `prev_state` is a list of event ids.
         """
         logger.debug("resolve_state_groups event_ids %s", event_ids)
 
@@ -251,9 +255,10 @@ class StateHandler(object):
 
     def _resolve_events(self, state_sets, event_type=None, state_key=""):
         """
-        :returns a tuple (new_state, prev_states). new_state is a map
-        from (type, state_key) to event. prev_states is a list of event_ids.
-        :rtype: (dict[(str, str), synapse.events.FrozenEvent], list[str])
+        Returns
+            (dict[(str, str), synapse.events.FrozenEvent], list[str]): a tuple
+            (new_state, prev_states). new_state is a map from (type, state_key)
+            to event. prev_states is a list of event_ids.
         """
         with Measure(self.clock, "state._resolve_events"):
             state = {}
diff --git a/synapse/storage/__init__.py b/synapse/storage/__init__.py
index aaad38039e..045ae6c03f 100644
--- a/synapse/storage/__init__.py
+++ b/synapse/storage/__init__.py
@@ -88,22 +88,17 @@ class DataStore(RoomMemberStore, RoomStore,
         self.hs = hs
         self.database_engine = hs.database_engine
 
-        cur = db_conn.cursor()
-        try:
-            cur.execute("SELECT MIN(stream_ordering) FROM events",)
-            rows = cur.fetchall()
-            self.min_stream_token = rows[0][0] if rows and rows[0] and rows[0][0] else -1
-            self.min_stream_token = min(self.min_stream_token, -1)
-        finally:
-            cur.close()
-
         self.client_ip_last_seen = Cache(
             name="client_ip_last_seen",
             keylen=4,
         )
 
         self._stream_id_gen = StreamIdGenerator(
-            db_conn, "events", "stream_ordering"
+            db_conn, "events", "stream_ordering",
+            extra_tables=[("local_invites", "stream_id")]
+        )
+        self._backfill_id_gen = StreamIdGenerator(
+            db_conn, "events", "stream_ordering", step=-1
         )
         self._receipts_id_gen = StreamIdGenerator(
             db_conn, "receipts_linearized", "stream_id"
@@ -129,7 +124,7 @@ class DataStore(RoomMemberStore, RoomStore,
             extra_tables=[("deleted_pushers", "stream_id")],
         )
 
-        events_max = self._stream_id_gen.get_max_token()
+        events_max = self._stream_id_gen.get_current_token()
         event_cache_prefill, min_event_val = self._get_cache_dict(
             db_conn, "events",
             entity_column="room_id",
@@ -145,7 +140,7 @@ class DataStore(RoomMemberStore, RoomStore,
             "MembershipStreamChangeCache", events_max,
         )
 
-        account_max = self._account_data_id_gen.get_max_token()
+        account_max = self._account_data_id_gen.get_current_token()
         self._account_data_stream_cache = StreamChangeCache(
             "AccountDataAndTagsChangeCache", account_max,
         )
@@ -156,7 +151,7 @@ class DataStore(RoomMemberStore, RoomStore,
             db_conn, "presence_stream",
             entity_column="user_id",
             stream_column="stream_id",
-            max_value=self._presence_id_gen.get_max_token(),
+            max_value=self._presence_id_gen.get_current_token(),
         )
         self.presence_stream_cache = StreamChangeCache(
             "PresenceStreamChangeCache", min_presence_val,
@@ -167,7 +162,7 @@ class DataStore(RoomMemberStore, RoomStore,
             db_conn, "push_rules_stream",
             entity_column="user_id",
             stream_column="stream_id",
-            max_value=self._push_rules_stream_id_gen.get_max_token()[0],
+            max_value=self._push_rules_stream_id_gen.get_current_token()[0],
         )
 
         self.push_rules_stream_cache = StreamChangeCache(
@@ -182,39 +177,6 @@ class DataStore(RoomMemberStore, RoomStore,
         self.__presence_on_startup = None
         return active_on_startup
 
-    def _get_cache_dict(self, db_conn, table, entity_column, stream_column, max_value):
-        # Fetch a mapping of room_id -> max stream position for "recent" rooms.
-        # It doesn't really matter how many we get, the StreamChangeCache will
-        # do the right thing to ensure it respects the max size of cache.
-        sql = (
-            "SELECT %(entity)s, MAX(%(stream)s) FROM %(table)s"
-            " WHERE %(stream)s > ? - 100000"
-            " GROUP BY %(entity)s"
-        ) % {
-            "table": table,
-            "entity": entity_column,
-            "stream": stream_column,
-        }
-
-        sql = self.database_engine.convert_param_style(sql)
-
-        txn = db_conn.cursor()
-        txn.execute(sql, (int(max_value),))
-        rows = txn.fetchall()
-        txn.close()
-
-        cache = {
-            row[0]: int(row[1])
-            for row in rows
-        }
-
-        if cache:
-            min_val = min(cache.values())
-        else:
-            min_val = max_value
-
-        return cache, min_val
-
     def _get_active_presence(self, db_conn):
         """Fetch non-offline presence from the database so that we can register
         the appropriate time outs.
diff --git a/synapse/storage/_base.py b/synapse/storage/_base.py
index b75b79df36..04d7fcf6d6 100644
--- a/synapse/storage/_base.py
+++ b/synapse/storage/_base.py
@@ -816,6 +816,40 @@ class SQLBaseStore(object):
             self._next_stream_id += 1
             return i
 
+    def _get_cache_dict(self, db_conn, table, entity_column, stream_column,
+                        max_value):
+        # Fetch a mapping of room_id -> max stream position for "recent" rooms.
+        # It doesn't really matter how many we get, the StreamChangeCache will
+        # do the right thing to ensure it respects the max size of cache.
+        sql = (
+            "SELECT %(entity)s, MAX(%(stream)s) FROM %(table)s"
+            " WHERE %(stream)s > ? - 100000"
+            " GROUP BY %(entity)s"
+        ) % {
+            "table": table,
+            "entity": entity_column,
+            "stream": stream_column,
+        }
+
+        sql = self.database_engine.convert_param_style(sql)
+
+        txn = db_conn.cursor()
+        txn.execute(sql, (int(max_value),))
+        rows = txn.fetchall()
+        txn.close()
+
+        cache = {
+            row[0]: int(row[1])
+            for row in rows
+        }
+
+        if cache:
+            min_val = min(cache.values())
+        else:
+            min_val = max_value
+
+        return cache, min_val
+
 
 class _RollbackButIsFineException(Exception):
     """ This exception is used to rollback a transaction without implying
diff --git a/synapse/storage/account_data.py b/synapse/storage/account_data.py
index faddefe219..7a7fbf1e52 100644
--- a/synapse/storage/account_data.py
+++ b/synapse/storage/account_data.py
@@ -200,7 +200,7 @@ class AccountDataStore(SQLBaseStore):
                 "add_room_account_data", add_account_data_txn, next_id
             )
 
-        result = self._account_data_id_gen.get_max_token()
+        result = self._account_data_id_gen.get_current_token()
         defer.returnValue(result)
 
     @defer.inlineCallbacks
@@ -239,7 +239,7 @@ class AccountDataStore(SQLBaseStore):
                 "add_user_account_data", add_account_data_txn, next_id
             )
 
-        result = self._account_data_id_gen.get_max_token()
+        result = self._account_data_id_gen.get_current_token()
         defer.returnValue(result)
 
     def _update_max_stream_id(self, txn, next_id):
diff --git a/synapse/storage/engines/__init__.py b/synapse/storage/engines/__init__.py
index a48230b93f..7bb5de1fe7 100644
--- a/synapse/storage/engines/__init__.py
+++ b/synapse/storage/engines/__init__.py
@@ -26,13 +26,13 @@ SUPPORTED_MODULE = {
 }
 
 
-def create_engine(config):
-    name = config.database_config["name"]
+def create_engine(database_config):
+    name = database_config["name"]
     engine_class = SUPPORTED_MODULE.get(name, None)
 
     if engine_class:
         module = importlib.import_module(name)
-        return engine_class(module, config=config)
+        return engine_class(module)
 
     raise RuntimeError(
         "Unsupported database engine '%s'" % (name,)
diff --git a/synapse/storage/engines/postgres.py b/synapse/storage/engines/postgres.py
index a09685b4df..c2290943b4 100644
--- a/synapse/storage/engines/postgres.py
+++ b/synapse/storage/engines/postgres.py
@@ -13,18 +13,15 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from synapse.storage.prepare_database import prepare_database
-
 from ._base import IncorrectDatabaseSetup
 
 
 class PostgresEngine(object):
     single_threaded = False
 
-    def __init__(self, database_module, config):
+    def __init__(self, database_module):
         self.module = database_module
         self.module.extensions.register_type(self.module.extensions.UNICODE)
-        self.config = config
 
     def check_database(self, txn):
         txn.execute("SHOW SERVER_ENCODING")
@@ -44,9 +41,6 @@ class PostgresEngine(object):
             self.module.extensions.ISOLATION_LEVEL_REPEATABLE_READ
         )
 
-    def prepare_database(self, db_conn):
-        prepare_database(db_conn, self, config=self.config)
-
     def is_deadlock(self, error):
         if isinstance(error, self.module.DatabaseError):
             return error.pgcode in ["40001", "40P01"]
diff --git a/synapse/storage/engines/sqlite3.py b/synapse/storage/engines/sqlite3.py
index 522b905949..14203aa500 100644
--- a/synapse/storage/engines/sqlite3.py
+++ b/synapse/storage/engines/sqlite3.py
@@ -13,9 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from synapse.storage.prepare_database import (
-    prepare_database, prepare_sqlite3_database
-)
+from synapse.storage.prepare_database import prepare_database
 
 import struct
 
@@ -23,9 +21,8 @@ import struct
 class Sqlite3Engine(object):
     single_threaded = True
 
-    def __init__(self, database_module, config):
+    def __init__(self, database_module):
         self.module = database_module
-        self.config = config
 
     def check_database(self, txn):
         pass
@@ -34,13 +31,9 @@ class Sqlite3Engine(object):
         return sql
 
     def on_new_connection(self, db_conn):
-        self.prepare_database(db_conn)
+        prepare_database(db_conn, self, config=None)
         db_conn.create_function("rank", 1, _rank)
 
-    def prepare_database(self, db_conn):
-        prepare_sqlite3_database(db_conn)
-        prepare_database(db_conn, self, config=self.config)
-
     def is_deadlock(self, error):
         return False
 
diff --git a/synapse/storage/event_federation.py b/synapse/storage/event_federation.py
index 3489315e0d..0827946207 100644
--- a/synapse/storage/event_federation.py
+++ b/synapse/storage/event_federation.py
@@ -163,6 +163,22 @@ class EventFederationStore(SQLBaseStore):
             room_id,
         )
 
+    @defer.inlineCallbacks
+    def get_max_depth_of_events(self, event_ids):
+        sql = (
+            "SELECT MAX(depth) FROM events WHERE event_id IN (%s)"
+        ) % (",".join(["?"] * len(event_ids)),)
+
+        rows = yield self._execute(
+            "get_max_depth_of_events", None,
+            sql, *event_ids
+        )
+
+        if rows:
+            defer.returnValue(rows[0][0])
+        else:
+            defer.returnValue(1)
+
     def _get_min_depth_interaction(self, txn, room_id):
         min_depth = self._simple_select_one_onecol_txn(
             txn,
diff --git a/synapse/storage/event_push_actions.py b/synapse/storage/event_push_actions.py
index dc5830450a..3933b6e2c5 100644
--- a/synapse/storage/event_push_actions.py
+++ b/synapse/storage/event_push_actions.py
@@ -26,8 +26,9 @@ logger = logging.getLogger(__name__)
 class EventPushActionsStore(SQLBaseStore):
     def _set_push_actions_for_event_and_users_txn(self, txn, event, tuples):
         """
-        :param event: the event set actions for
-        :param tuples: list of tuples of (user_id, actions)
+        Args:
+            event: the event set actions for
+            tuples: list of tuples of (user_id, actions)
         """
         values = []
         for uid, actions in tuples:
diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index e0ef7f46b2..ee87a71719 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -24,8 +24,7 @@ from synapse.util.logutils import log_function
 from synapse.api.constants import EventTypes
 
 from canonicaljson import encode_canonical_json
-from contextlib import contextmanager
-
+from collections import namedtuple
 
 import logging
 import math
@@ -61,20 +60,14 @@ class EventsStore(SQLBaseStore):
         )
 
     @defer.inlineCallbacks
-    def persist_events(self, events_and_contexts, backfilled=False,
-                       is_new_state=True):
+    def persist_events(self, events_and_contexts, backfilled=False):
         if not events_and_contexts:
             return
 
         if backfilled:
-            start = self.min_stream_token - 1
-            self.min_stream_token -= len(events_and_contexts) + 1
-            stream_orderings = range(start, self.min_stream_token, -1)
-
-            @contextmanager
-            def stream_ordering_manager():
-                yield stream_orderings
-            stream_ordering_manager = stream_ordering_manager()
+            stream_ordering_manager = self._backfill_id_gen.get_next_mult(
+                len(events_and_contexts)
+            )
         else:
             stream_ordering_manager = self._stream_id_gen.get_next_mult(
                 len(events_and_contexts)
@@ -110,13 +103,11 @@ class EventsStore(SQLBaseStore):
                         self._persist_events_txn,
                         events_and_contexts=chunk,
                         backfilled=backfilled,
-                        is_new_state=is_new_state,
                     )
 
     @defer.inlineCallbacks
     @log_function
-    def persist_event(self, event, context,
-                      is_new_state=True, current_state=None):
+    def persist_event(self, event, context, current_state=None):
 
         try:
             with self._stream_id_gen.get_next() as stream_ordering:
@@ -128,13 +119,12 @@ class EventsStore(SQLBaseStore):
                         self._persist_event_txn,
                         event=event,
                         context=context,
-                        is_new_state=is_new_state,
                         current_state=current_state,
                     )
         except _RollbackButIsFineException:
             pass
 
-        max_persisted_id = yield self._stream_id_gen.get_max_token()
+        max_persisted_id = yield self._stream_id_gen.get_current_token()
         defer.returnValue((stream_ordering, max_persisted_id))
 
     @defer.inlineCallbacks
@@ -194,8 +184,7 @@ class EventsStore(SQLBaseStore):
         defer.returnValue({e.event_id: e for e in events})
 
     @log_function
-    def _persist_event_txn(self, txn, event, context,
-                           is_new_state, current_state):
+    def _persist_event_txn(self, txn, event, context, current_state):
         # We purposefully do this first since if we include a `current_state`
         # key, we *want* to update the `current_state_events` table
         if current_state:
@@ -203,7 +192,16 @@ class EventsStore(SQLBaseStore):
             txn.call_after(self.get_rooms_for_user.invalidate_all)
             txn.call_after(self.get_users_in_room.invalidate, (event.room_id,))
             txn.call_after(self.get_joined_hosts_for_room.invalidate, (event.room_id,))
-            txn.call_after(self.get_room_name_and_aliases, event.room_id)
+            txn.call_after(self.get_room_name_and_aliases.invalidate, (event.room_id,))
+
+            # Add an entry to the current_state_resets table to record the point
+            # where we clobbered the current state
+            stream_order = event.internal_metadata.stream_ordering
+            self._simple_insert_txn(
+                txn,
+                table="current_state_resets",
+                values={"event_stream_ordering": stream_order}
+            )
 
             self._simple_delete_txn(
                 txn,
@@ -227,12 +225,10 @@ class EventsStore(SQLBaseStore):
             txn,
             [(event, context)],
             backfilled=False,
-            is_new_state=is_new_state,
         )
 
     @log_function
-    def _persist_events_txn(self, txn, events_and_contexts, backfilled,
-                            is_new_state):
+    def _persist_events_txn(self, txn, events_and_contexts, backfilled):
         depth_updates = {}
         for event, context in events_and_contexts:
             # Remove the any existing cache entries for the event_ids
@@ -314,6 +310,18 @@ class EventsStore(SQLBaseStore):
                     (metadata_json, event.event_id,)
                 )
 
+                stream_order = event.internal_metadata.stream_ordering
+                state_group_id = context.state_group or context.new_state_group_id
+                self._simple_insert_txn(
+                    txn,
+                    table="ex_outlier_stream",
+                    values={
+                        "event_stream_ordering": stream_order,
+                        "event_id": event.event_id,
+                        "state_group": state_group_id,
+                    }
+                )
+
                 sql = (
                     "UPDATE events SET outlier = ?"
                     " WHERE event_id = ?"
@@ -359,7 +367,8 @@ class EventsStore(SQLBaseStore):
                 event
                 for event, _ in events_and_contexts
                 if event.type == EventTypes.Member
-            ]
+            ],
+            backfilled=backfilled,
         )
 
         def event_dict(event):
@@ -431,10 +440,9 @@ class EventsStore(SQLBaseStore):
             txn, [event for event, _ in events_and_contexts]
         )
 
-        state_events_and_contexts = filter(
-            lambda i: i[0].is_state(),
-            events_and_contexts,
-        )
+        state_events_and_contexts = [
+            ec for ec in events_and_contexts if ec[0].is_state()
+        ]
 
         state_values = []
         for event, context in state_events_and_contexts:
@@ -472,32 +480,44 @@ class EventsStore(SQLBaseStore):
             ],
         )
 
-        if is_new_state:
-            for event, _ in state_events_and_contexts:
-                if not context.rejected:
-                    txn.call_after(
-                        self._get_current_state_for_key.invalidate,
-                        (event.room_id, event.type, event.state_key,)
-                    )
+        if backfilled:
+            # Backfilled events come before the current state so we don't need
+            # to update the current state table
+            return
 
-                    if event.type in [EventTypes.Name, EventTypes.Aliases]:
-                        txn.call_after(
-                            self.get_room_name_and_aliases.invalidate,
-                            (event.room_id,)
-                        )
-
-                    self._simple_upsert_txn(
-                        txn,
-                        "current_state_events",
-                        keyvalues={
-                            "room_id": event.room_id,
-                            "type": event.type,
-                            "state_key": event.state_key,
-                        },
-                        values={
-                            "event_id": event.event_id,
-                        }
-                    )
+        for event, _ in state_events_and_contexts:
+            if event.internal_metadata.is_outlier():
+                # Outlier events shouldn't clobber the current state.
+                continue
+
+            if context.rejected:
+                # If the event failed it's auth checks then it shouldn't
+                # clobbler the current state.
+                continue
+
+            txn.call_after(
+                self._get_current_state_for_key.invalidate,
+                (event.room_id, event.type, event.state_key,)
+            )
+
+            if event.type in [EventTypes.Name, EventTypes.Aliases]:
+                txn.call_after(
+                    self.get_room_name_and_aliases.invalidate,
+                    (event.room_id,)
+                )
+
+            self._simple_upsert_txn(
+                txn,
+                "current_state_events",
+                keyvalues={
+                    "room_id": event.room_id,
+                    "type": event.type,
+                    "state_key": event.state_key,
+                },
+                values={
+                    "event_id": event.event_id,
+                }
+            )
 
         return
 
@@ -1086,10 +1106,7 @@ class EventsStore(SQLBaseStore):
 
     def get_current_backfill_token(self):
         """The current minimum token that backfilled events have reached"""
-
-        # TODO: Fix race with the persit_event txn by using one of the
-        # stream id managers
-        return -self.min_stream_token
+        return -self._backfill_id_gen.get_current_token()
 
     def get_all_new_events(self, last_backfill_id, last_forward_id,
                            current_backfill_id, current_forward_id, limit):
@@ -1110,8 +1127,34 @@ class EventsStore(SQLBaseStore):
             if last_forward_id != current_forward_id:
                 txn.execute(sql, (last_forward_id, current_forward_id, limit))
                 new_forward_events = txn.fetchall()
+
+                if len(new_forward_events) == limit:
+                    upper_bound = new_forward_events[-1][0]
+                else:
+                    upper_bound = current_forward_id
+
+                sql = (
+                    "SELECT event_stream_ordering FROM current_state_resets"
+                    " WHERE ? < event_stream_ordering"
+                    " AND event_stream_ordering <= ?"
+                    " ORDER BY event_stream_ordering ASC"
+                )
+                txn.execute(sql, (last_forward_id, upper_bound))
+                state_resets = txn.fetchall()
+
+                sql = (
+                    "SELECT event_stream_ordering, event_id, state_group"
+                    " FROM ex_outlier_stream"
+                    " WHERE ? > event_stream_ordering"
+                    " AND event_stream_ordering >= ?"
+                    " ORDER BY event_stream_ordering DESC"
+                )
+                txn.execute(sql, (last_forward_id, upper_bound))
+                forward_ex_outliers = txn.fetchall()
             else:
                 new_forward_events = []
+                state_resets = []
+                forward_ex_outliers = []
 
             sql = (
                 "SELECT -e.stream_ordering, ej.internal_metadata, ej.json,"
@@ -1128,8 +1171,35 @@ class EventsStore(SQLBaseStore):
             if last_backfill_id != current_backfill_id:
                 txn.execute(sql, (-last_backfill_id, -current_backfill_id, limit))
                 new_backfill_events = txn.fetchall()
+
+                if len(new_backfill_events) == limit:
+                    upper_bound = new_backfill_events[-1][0]
+                else:
+                    upper_bound = current_backfill_id
+
+                sql = (
+                    "SELECT -event_stream_ordering, event_id, state_group"
+                    " FROM ex_outlier_stream"
+                    " WHERE ? > event_stream_ordering"
+                    " AND event_stream_ordering >= ?"
+                    " ORDER BY event_stream_ordering DESC"
+                )
+                txn.execute(sql, (-last_backfill_id, -upper_bound))
+                backward_ex_outliers = txn.fetchall()
             else:
                 new_backfill_events = []
+                backward_ex_outliers = []
 
-            return (new_forward_events, new_backfill_events)
+            return AllNewEventsResult(
+                new_forward_events, new_backfill_events,
+                forward_ex_outliers, backward_ex_outliers,
+                state_resets,
+            )
         return self.runInteraction("get_all_new_events", get_all_new_events_txn)
+
+
+AllNewEventsResult = namedtuple("AllNewEventsResult", [
+    "new_forward_events", "new_backfill_events",
+    "forward_ex_outliers", "backward_ex_outliers",
+    "state_resets"
+])
diff --git a/synapse/storage/prepare_database.py b/synapse/storage/prepare_database.py
index 3f29aad1e8..00833422af 100644
--- a/synapse/storage/prepare_database.py
+++ b/synapse/storage/prepare_database.py
@@ -25,7 +25,7 @@ logger = logging.getLogger(__name__)
 
 # Remember to update this number every time a change is made to database
 # schema files, so the users will be informed on server restarts.
-SCHEMA_VERSION = 30
+SCHEMA_VERSION = 31
 
 dir_path = os.path.abspath(os.path.dirname(__file__))
 
@@ -53,6 +53,9 @@ class UpgradeDatabaseException(PrepareDatabaseException):
 def prepare_database(db_conn, database_engine, config):
     """Prepares a database for usage. Will either create all necessary tables
     or upgrade from an older schema version.
+
+    If `config` is None then prepare_database will assert that no upgrade is
+    necessary, *or* will create a fresh database if the database is empty.
     """
     try:
         cur = db_conn.cursor()
@@ -60,13 +63,18 @@ def prepare_database(db_conn, database_engine, config):
 
         if version_info:
             user_version, delta_files, upgraded = version_info
-            _upgrade_existing_database(
-                cur, user_version, delta_files, upgraded, database_engine, config
-            )
-        else:
-            _setup_new_database(cur, database_engine, config)
 
-        # cur.execute("PRAGMA user_version = %d" % (SCHEMA_VERSION,))
+            if config is None:
+                if user_version != SCHEMA_VERSION:
+                    # If we don't pass in a config file then we are expecting to
+                    # have already upgraded the DB.
+                    raise UpgradeDatabaseException("Database needs to be upgraded")
+            else:
+                _upgrade_existing_database(
+                    cur, user_version, delta_files, upgraded, database_engine, config
+                )
+        else:
+            _setup_new_database(cur, database_engine)
 
         cur.close()
         db_conn.commit()
@@ -75,7 +83,7 @@ def prepare_database(db_conn, database_engine, config):
         raise
 
 
-def _setup_new_database(cur, database_engine, config):
+def _setup_new_database(cur, database_engine):
     """Sets up the database by finding a base set of "full schemas" and then
     applying any necessary deltas.
 
@@ -148,12 +156,13 @@ def _setup_new_database(cur, database_engine, config):
         applied_delta_files=[],
         upgraded=False,
         database_engine=database_engine,
-        config=config,
+        config=None,
+        is_empty=True,
     )
 
 
 def _upgrade_existing_database(cur, current_version, applied_delta_files,
-                               upgraded, database_engine, config):
+                               upgraded, database_engine, config, is_empty=False):
     """Upgrades an existing database.
 
     Delta files can either be SQL stored in *.sql files, or python modules
@@ -246,7 +255,9 @@ def _upgrade_existing_database(cur, current_version, applied_delta_files,
                         module_name, absolute_path, python_file
                     )
                 logger.debug("Running script %s", relative_path)
-                module.run_upgrade(cur, database_engine, config=config)
+                module.run_create(cur, database_engine)
+                if not is_empty:
+                    module.run_upgrade(cur, database_engine, config=config)
             elif ext == ".pyc":
                 # Sometimes .pyc files turn up anyway even though we've
                 # disabled their generation; e.g. from distribution package
@@ -361,36 +372,3 @@ def _get_or_create_schema_state(txn, database_engine):
         return current_version, applied_deltas, upgraded
 
     return None
-
-
-def prepare_sqlite3_database(db_conn):
-    """This function should be called before `prepare_database` on sqlite3
-    databases.
-
-    Since we changed the way we store the current schema version and handle
-    updates to schemas, we need a way to upgrade from the old method to the
-    new. This only affects sqlite databases since they were the only ones
-    supported at the time.
-    """
-    with db_conn:
-        schema_path = os.path.join(
-            dir_path, "schema", "schema_version.sql",
-        )
-        create_schema = read_schema(schema_path)
-        db_conn.executescript(create_schema)
-
-        c = db_conn.execute("SELECT * FROM schema_version")
-        rows = c.fetchall()
-        c.close()
-
-        if not rows:
-            c = db_conn.execute("PRAGMA user_version")
-            row = c.fetchone()
-            c.close()
-
-            if row and row[0]:
-                db_conn.execute(
-                    "REPLACE INTO schema_version (version, upgraded)"
-                    " VALUES (?,?)",
-                    (row[0], False)
-                )
diff --git a/synapse/storage/presence.py b/synapse/storage/presence.py
index 4cec31e316..59b4ef5ce6 100644
--- a/synapse/storage/presence.py
+++ b/synapse/storage/presence.py
@@ -68,7 +68,9 @@ class PresenceStore(SQLBaseStore):
                 self._update_presence_txn, stream_orderings, presence_states,
             )
 
-        defer.returnValue((stream_orderings[-1], self._presence_id_gen.get_max_token()))
+        defer.returnValue((
+            stream_orderings[-1], self._presence_id_gen.get_current_token()
+        ))
 
     def _update_presence_txn(self, txn, stream_orderings, presence_states):
         for stream_id, state in zip(stream_orderings, presence_states):
@@ -155,7 +157,7 @@ class PresenceStore(SQLBaseStore):
         defer.returnValue([UserPresenceState(**row) for row in rows])
 
     def get_current_presence_token(self):
-        return self._presence_id_gen.get_max_token()
+        return self._presence_id_gen.get_current_token()
 
     def allow_presence_visible(self, observed_localpart, observer_userid):
         return self._simple_insert(
diff --git a/synapse/storage/push_rule.py b/synapse/storage/push_rule.py
index 9dbad2fd5f..d2bf7f2aec 100644
--- a/synapse/storage/push_rule.py
+++ b/synapse/storage/push_rule.py
@@ -392,7 +392,7 @@ class PushRuleStore(SQLBaseStore):
         """Get the position of the push rules stream.
         Returns a pair of a stream id for the push_rules stream and the
         room stream ordering it corresponds to."""
-        return self._push_rules_stream_id_gen.get_max_token()
+        return self._push_rules_stream_id_gen.get_current_token()
 
     def have_push_rules_changed_for_user(self, user_id, last_id):
         if not self.push_rules_stream_cache.has_entity_changed(user_id, last_id):
diff --git a/synapse/storage/pusher.py b/synapse/storage/pusher.py
index 87b2ac5773..d1669c778a 100644
--- a/synapse/storage/pusher.py
+++ b/synapse/storage/pusher.py
@@ -78,7 +78,7 @@ class PusherStore(SQLBaseStore):
         defer.returnValue(rows)
 
     def get_pushers_stream_token(self):
-        return self._pushers_id_gen.get_max_token()
+        return self._pushers_id_gen.get_current_token()
 
     def get_all_updated_pushers(self, last_id, current_id, limit):
         def get_all_updated_pushers_txn(txn):
diff --git a/synapse/storage/receipts.py b/synapse/storage/receipts.py
index 6b9d848eaa..7fdd84bbdc 100644
--- a/synapse/storage/receipts.py
+++ b/synapse/storage/receipts.py
@@ -31,7 +31,7 @@ class ReceiptsStore(SQLBaseStore):
         super(ReceiptsStore, self).__init__(hs)
 
         self._receipts_stream_cache = StreamChangeCache(
-            "ReceiptsRoomChangeCache", self._receipts_id_gen.get_max_token()
+            "ReceiptsRoomChangeCache", self._receipts_id_gen.get_current_token()
         )
 
     @cached(num_args=2)
@@ -160,8 +160,8 @@ class ReceiptsStore(SQLBaseStore):
             "content": content,
         }])
 
-    @cachedList(cache=get_linearized_receipts_for_room.cache, list_name="room_ids",
-                num_args=3, inlineCallbacks=True)
+    @cachedList(cached_method_name="get_linearized_receipts_for_room",
+                list_name="room_ids", num_args=3, inlineCallbacks=True)
     def _get_linearized_receipts_for_rooms(self, room_ids, to_key, from_key=None):
         if not room_ids:
             defer.returnValue({})
@@ -221,7 +221,7 @@ class ReceiptsStore(SQLBaseStore):
         defer.returnValue(results)
 
     def get_max_receipt_stream_id(self):
-        return self._receipts_id_gen.get_max_token()
+        return self._receipts_id_gen.get_current_token()
 
     def insert_linearized_receipt_txn(self, txn, room_id, receipt_type,
                                       user_id, event_id, data, stream_id):
@@ -346,7 +346,7 @@ class ReceiptsStore(SQLBaseStore):
             room_id, receipt_type, user_id, event_ids, data
         )
 
-        max_persisted_id = self._stream_id_gen.get_max_token()
+        max_persisted_id = self._stream_id_gen.get_current_token()
 
         defer.returnValue((stream_id, max_persisted_id))
 
diff --git a/synapse/storage/registration.py b/synapse/storage/registration.py
index bd4eb88a92..1f71773aaa 100644
--- a/synapse/storage/registration.py
+++ b/synapse/storage/registration.py
@@ -319,7 +319,7 @@ class RegistrationStore(SQLBaseStore):
 
         defer.returnValue(res if res else False)
 
-    @cachedList(cache=is_guest.cache, list_name="user_ids", num_args=1,
+    @cachedList(cached_method_name="is_guest", list_name="user_ids", num_args=1,
                 inlineCallbacks=True)
     def are_guests(self, user_ids):
         sql = "SELECT name, is_guest FROM users WHERE name IN (%s)" % (
@@ -458,12 +458,15 @@ class RegistrationStore(SQLBaseStore):
         """
         Gets the 3pid's guest access token if exists, else saves access_token.
 
-        :param medium (str): Medium of the 3pid. Must be "email".
-        :param address (str): 3pid address.
-        :param access_token (str): The access token to persist if none is
-            already persisted.
-        :param inviter_user_id (str): User ID of the inviter.
-        :return (deferred str): Whichever access token is persisted at the end
+        Args:
+            medium (str): Medium of the 3pid. Must be "email".
+            address (str): 3pid address.
+            access_token (str): The access token to persist if none is
+                already persisted.
+            inviter_user_id (str): User ID of the inviter.
+
+        Returns:
+            deferred str: Whichever access token is persisted at the end
             of this function call.
         """
         def insert(txn):
diff --git a/synapse/storage/roommember.py b/synapse/storage/roommember.py
index 430b49c12e..66e7a40e3c 100644
--- a/synapse/storage/roommember.py
+++ b/synapse/storage/roommember.py
@@ -36,7 +36,7 @@ RoomsForUser = namedtuple(
 
 class RoomMemberStore(SQLBaseStore):
 
-    def _store_room_members_txn(self, txn, events):
+    def _store_room_members_txn(self, txn, events, backfilled):
         """Store a room member in the database.
         """
         self._simple_insert_many_txn(
@@ -62,6 +62,64 @@ class RoomMemberStore(SQLBaseStore):
                 self._membership_stream_cache.entity_has_changed,
                 event.state_key, event.internal_metadata.stream_ordering
             )
+            txn.call_after(
+                self.get_invited_rooms_for_user.invalidate, (event.state_key,)
+            )
+
+            # We update the local_invites table only if the event is "current",
+            # i.e., its something that has just happened.
+            # The only current event that can also be an outlier is if its an
+            # invite that has come in across federation.
+            is_new_state = not backfilled and (
+                not event.internal_metadata.is_outlier()
+                or event.internal_metadata.is_invite_from_remote()
+            )
+            is_mine = self.hs.is_mine_id(event.state_key)
+            if is_new_state and is_mine:
+                if event.membership == Membership.INVITE:
+                    self._simple_insert_txn(
+                        txn,
+                        table="local_invites",
+                        values={
+                            "event_id": event.event_id,
+                            "invitee": event.state_key,
+                            "inviter": event.sender,
+                            "room_id": event.room_id,
+                            "stream_id": event.internal_metadata.stream_ordering,
+                        }
+                    )
+                else:
+                    sql = (
+                        "UPDATE local_invites SET stream_id = ?, replaced_by = ? WHERE"
+                        " room_id = ? AND invitee = ? AND locally_rejected is NULL"
+                        " AND replaced_by is NULL"
+                    )
+
+                    txn.execute(sql, (
+                        event.internal_metadata.stream_ordering,
+                        event.event_id,
+                        event.room_id,
+                        event.state_key,
+                    ))
+
+    @defer.inlineCallbacks
+    def locally_reject_invite(self, user_id, room_id):
+        sql = (
+            "UPDATE local_invites SET stream_id = ?, locally_rejected = ? WHERE"
+            " room_id = ? AND invitee = ? AND locally_rejected is NULL"
+            " AND replaced_by is NULL"
+        )
+
+        def f(txn, stream_ordering):
+            txn.execute(sql, (
+                stream_ordering,
+                True,
+                room_id,
+                user_id,
+            ))
+
+        with self._stream_id_gen.get_next() as stream_ordering:
+            yield self.runInteraction("locally_reject_invite", f, stream_ordering)
 
     def get_room_member(self, user_id, room_id):
         """Retrieve the current state of a room member.
@@ -127,6 +185,24 @@ class RoomMemberStore(SQLBaseStore):
             user_id, [Membership.INVITE]
         )
 
+    @defer.inlineCallbacks
+    def get_invite_for_user_in_room(self, user_id, room_id):
+        """Gets the invite for the given user and room
+
+        Args:
+            user_id (str)
+            room_id (str)
+
+        Returns:
+            Deferred: Resolves to either a RoomsForUser or None if no invite was
+                found.
+        """
+        invites = yield self.get_invited_rooms_for_user(user_id)
+        for invite in invites:
+            if invite.room_id == room_id:
+                defer.returnValue(invite)
+        defer.returnValue(None)
+
     def get_leave_and_ban_events_for_user(self, user_id):
         """ Get all the leave events for a user
         Args:
@@ -163,29 +239,55 @@ class RoomMemberStore(SQLBaseStore):
 
     def _get_rooms_for_user_where_membership_is_txn(self, txn, user_id,
                                                     membership_list):
-        where_clause = "user_id = ? AND (%s) AND forgotten = 0" % (
-            " OR ".join(["membership = ?" for _ in membership_list]),
-        )
 
-        args = [user_id]
-        args.extend(membership_list)
+        do_invite = Membership.INVITE in membership_list
+        membership_list = [m for m in membership_list if m != Membership.INVITE]
 
-        sql = (
-            "SELECT m.room_id, m.sender, m.membership, m.event_id, e.stream_ordering"
-            " FROM current_state_events as c"
-            " INNER JOIN room_memberships as m"
-            " ON m.event_id = c.event_id"
-            " INNER JOIN events as e"
-            " ON e.event_id = c.event_id"
-            " AND m.room_id = c.room_id"
-            " AND m.user_id = c.state_key"
-            " WHERE %s"
-        ) % (where_clause,)
+        results = []
+        if membership_list:
+            where_clause = "user_id = ? AND (%s) AND forgotten = 0" % (
+                " OR ".join(["membership = ?" for _ in membership_list]),
+            )
+
+            args = [user_id]
+            args.extend(membership_list)
+
+            sql = (
+                "SELECT m.room_id, m.sender, m.membership, m.event_id, e.stream_ordering"
+                " FROM current_state_events as c"
+                " INNER JOIN room_memberships as m"
+                " ON m.event_id = c.event_id"
+                " INNER JOIN events as e"
+                " ON e.event_id = c.event_id"
+                " AND m.room_id = c.room_id"
+                " AND m.user_id = c.state_key"
+                " WHERE %s"
+            ) % (where_clause,)
+
+            txn.execute(sql, args)
+            results = [
+                RoomsForUser(**r) for r in self.cursor_to_dict(txn)
+            ]
+
+        if do_invite:
+            sql = (
+                "SELECT i.room_id, inviter, i.event_id, e.stream_ordering"
+                " FROM local_invites as i"
+                " INNER JOIN events as e USING (event_id)"
+                " WHERE invitee = ? AND locally_rejected is NULL"
+                " AND replaced_by is NULL"
+            )
+
+            txn.execute(sql, (user_id,))
+            results.extend(RoomsForUser(
+                room_id=r["room_id"],
+                sender=r["inviter"],
+                event_id=r["event_id"],
+                stream_ordering=r["stream_ordering"],
+                membership=Membership.INVITE,
+            ) for r in self.cursor_to_dict(txn))
 
-        txn.execute(sql, args)
-        return [
-            RoomsForUser(**r) for r in self.cursor_to_dict(txn)
-        ]
+        return results
 
     @cached(max_entries=5000)
     def get_joined_hosts_for_room(self, room_id):
diff --git a/synapse/storage/schema/delta/14/upgrade_appservice_db.py b/synapse/storage/schema/delta/14/upgrade_appservice_db.py
index 5c40a77757..8755bb2e49 100644
--- a/synapse/storage/schema/delta/14/upgrade_appservice_db.py
+++ b/synapse/storage/schema/delta/14/upgrade_appservice_db.py
@@ -18,7 +18,7 @@ import logging
 logger = logging.getLogger(__name__)
 
 
-def run_upgrade(cur, *args, **kwargs):
+def run_create(cur, *args, **kwargs):
     cur.execute("SELECT id, regex FROM application_services_regex")
     for row in cur.fetchall():
         try:
@@ -35,3 +35,7 @@ def run_upgrade(cur, *args, **kwargs):
                 "UPDATE application_services_regex SET regex=? WHERE id=?",
                 (new_regex, row[0])
             )
+
+
+def run_upgrade(*args, **kwargs):
+    pass
diff --git a/synapse/storage/schema/delta/20/pushers.py b/synapse/storage/schema/delta/20/pushers.py
index 29164732af..147496a38b 100644
--- a/synapse/storage/schema/delta/20/pushers.py
+++ b/synapse/storage/schema/delta/20/pushers.py
@@ -27,7 +27,7 @@ import logging
 logger = logging.getLogger(__name__)
 
 
-def run_upgrade(cur, database_engine, *args, **kwargs):
+def run_create(cur, database_engine, *args, **kwargs):
     logger.info("Porting pushers table...")
     cur.execute("""
         CREATE TABLE IF NOT EXISTS pushers2 (
@@ -74,3 +74,7 @@ def run_upgrade(cur, database_engine, *args, **kwargs):
     cur.execute("DROP TABLE pushers")
     cur.execute("ALTER TABLE pushers2 RENAME TO pushers")
     logger.info("Moved %d pushers to new table", count)
+
+
+def run_upgrade(*args, **kwargs):
+    pass
diff --git a/synapse/storage/schema/delta/25/fts.py b/synapse/storage/schema/delta/25/fts.py
index d3ff2b1779..4269ac69ad 100644
--- a/synapse/storage/schema/delta/25/fts.py
+++ b/synapse/storage/schema/delta/25/fts.py
@@ -43,7 +43,7 @@ SQLITE_TABLE = (
 )
 
 
-def run_upgrade(cur, database_engine, *args, **kwargs):
+def run_create(cur, database_engine, *args, **kwargs):
     if isinstance(database_engine, PostgresEngine):
         for statement in get_statements(POSTGRES_TABLE.splitlines()):
             cur.execute(statement)
@@ -76,3 +76,7 @@ def run_upgrade(cur, database_engine, *args, **kwargs):
         sql = database_engine.convert_param_style(sql)
 
         cur.execute(sql, ("event_search", progress_json))
+
+
+def run_upgrade(*args, **kwargs):
+    pass
diff --git a/synapse/storage/schema/delta/27/ts.py b/synapse/storage/schema/delta/27/ts.py
index f8c16391a2..71b12a2731 100644
--- a/synapse/storage/schema/delta/27/ts.py
+++ b/synapse/storage/schema/delta/27/ts.py
@@ -27,7 +27,7 @@ ALTER_TABLE = (
 )
 
 
-def run_upgrade(cur, database_engine, *args, **kwargs):
+def run_create(cur, database_engine, *args, **kwargs):
     for statement in get_statements(ALTER_TABLE.splitlines()):
         cur.execute(statement)
 
@@ -55,3 +55,7 @@ def run_upgrade(cur, database_engine, *args, **kwargs):
         sql = database_engine.convert_param_style(sql)
 
         cur.execute(sql, ("event_origin_server_ts", progress_json))
+
+
+def run_upgrade(*args, **kwargs):
+    pass
diff --git a/synapse/storage/schema/delta/30/as_users.py b/synapse/storage/schema/delta/30/as_users.py
index 4f6e9dd540..b417e3ac08 100644
--- a/synapse/storage/schema/delta/30/as_users.py
+++ b/synapse/storage/schema/delta/30/as_users.py
@@ -18,7 +18,7 @@ from synapse.storage.appservice import ApplicationServiceStore
 logger = logging.getLogger(__name__)
 
 
-def run_upgrade(cur, database_engine, config, *args, **kwargs):
+def run_create(cur, database_engine, *args, **kwargs):
     # NULL indicates user was not registered by an appservice.
     try:
         cur.execute("ALTER TABLE users ADD COLUMN appservice_id TEXT")
@@ -26,6 +26,8 @@ def run_upgrade(cur, database_engine, config, *args, **kwargs):
         # Maybe we already added the column? Hope so...
         pass
 
+
+def run_upgrade(cur, database_engine, config, *args, **kwargs):
     cur.execute("SELECT name FROM users")
     rows = cur.fetchall()
 
diff --git a/synapse/storage/schema/delta/30/state_stream.sql b/synapse/storage/schema/delta/30/state_stream.sql
new file mode 100644
index 0000000000..706fe1dcf4
--- /dev/null
+++ b/synapse/storage/schema/delta/30/state_stream.sql
@@ -0,0 +1,38 @@
+/* Copyright 2016 OpenMarket Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+/**
+ * The positions in the event stream_ordering when the current_state was
+ * replaced by the state at the event.
+ */
+
+CREATE TABLE IF NOT EXISTS current_state_resets(
+    event_stream_ordering BIGINT PRIMARY KEY NOT NULL
+);
+
+/* The outlier events that have aquired a state group typically through
+ * backfill. This is tracked separately to the events table, as assigning a
+ * state group change the position of the existing event in the stream
+ * ordering.
+ * However since a stream_ordering is assigned in persist_event for the
+ * (event, state) pair, we can use that stream_ordering to identify when
+ * the new state was assigned for the event.
+ */
+CREATE TABLE IF NOT EXISTS ex_outlier_stream(
+    event_stream_ordering BIGINT PRIMARY KEY NOT NULL,
+    event_id TEXT NOT NULL,
+    state_group BIGINT NOT NULL
+);
diff --git a/synapse/storage/schema/delta/31/invites.sql b/synapse/storage/schema/delta/31/invites.sql
new file mode 100644
index 0000000000..2c57846d5a
--- /dev/null
+++ b/synapse/storage/schema/delta/31/invites.sql
@@ -0,0 +1,42 @@
+/* Copyright 2016 OpenMarket Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+CREATE TABLE local_invites(
+    stream_id BIGINT NOT NULL,
+    inviter TEXT NOT NULL,
+    invitee TEXT NOT NULL,
+    event_id TEXT NOT NULL,
+    room_id TEXT NOT NULL,
+    locally_rejected TEXT,
+    replaced_by TEXT
+);
+
+-- Insert all invites for local users into new `invites` table
+INSERT INTO local_invites SELECT
+        stream_ordering as stream_id,
+        sender as inviter,
+        state_key as invitee,
+        event_id,
+        room_id,
+        NULL as locally_rejected,
+        NULL as replaced_by
+    FROM events
+    NATURAL JOIN current_state_events
+    NATURAL JOIN room_memberships
+    WHERE membership = 'invite'  AND state_key IN (SELECT name FROM users);
+
+CREATE INDEX local_invites_id ON local_invites(stream_id);
+CREATE INDEX local_invites_for_user_idx ON local_invites(invitee, locally_rejected, replaced_by, room_id);
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index 7fc9a4f264..c5d2a3a6df 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -249,11 +249,14 @@ class StateStore(SQLBaseStore):
         """
         Get the state dict corresponding to a particular event
 
-        :param str event_id: event whose state should be returned
-        :param list[(str, str)]|None types: List of (type, state_key) tuples
-            which are used to filter the state fetched. May be None, which
-            matches any key
-        :return: a deferred dict from (type, state_key) -> state_event
+        Args:
+            event_id(str): event whose state should be returned
+            types(list[(str, str)]|None): List of (type, state_key) tuples
+                which are used to filter the state fetched. May be None, which
+                matches any key
+
+        Returns:
+            A deferred dict from (type, state_key) -> state_event
         """
         state_map = yield self.get_state_for_events([event_id], types)
         defer.returnValue(state_map[event_id])
@@ -270,8 +273,8 @@ class StateStore(SQLBaseStore):
             desc="_get_state_group_for_event",
         )
 
-    @cachedList(cache=_get_state_group_for_event.cache, list_name="event_ids",
-                num_args=1, inlineCallbacks=True)
+    @cachedList(cached_method_name="_get_state_group_for_event",
+                list_name="event_ids", num_args=1, inlineCallbacks=True)
     def _get_state_group_for_events(self, event_ids):
         """Returns mapping event_id -> state_group
         """
@@ -458,4 +461,4 @@ class StateStore(SQLBaseStore):
         )
 
     def get_state_stream_token(self):
-        return self._state_groups_id_gen.get_max_token()
+        return self._state_groups_id_gen.get_current_token()
diff --git a/synapse/storage/stream.py b/synapse/storage/stream.py
index cf84938be5..76bcd9cd00 100644
--- a/synapse/storage/stream.py
+++ b/synapse/storage/stream.py
@@ -539,7 +539,7 @@ class StreamStore(SQLBaseStore):
 
     @defer.inlineCallbacks
     def get_room_events_max_id(self, direction='f'):
-        token = yield self._stream_id_gen.get_max_token()
+        token = yield self._stream_id_gen.get_current_token()
         if direction != 'b':
             defer.returnValue("s%d" % (token,))
         else:
diff --git a/synapse/storage/tags.py b/synapse/storage/tags.py
index a0e6b42b30..9da23f34cb 100644
--- a/synapse/storage/tags.py
+++ b/synapse/storage/tags.py
@@ -30,7 +30,7 @@ class TagsStore(SQLBaseStore):
         Returns:
             A deferred int.
         """
-        return self._account_data_id_gen.get_max_token()
+        return self._account_data_id_gen.get_current_token()
 
     @cached()
     def get_tags_for_user(self, user_id):
@@ -200,7 +200,7 @@ class TagsStore(SQLBaseStore):
 
         self.get_tags_for_user.invalidate((user_id,))
 
-        result = self._account_data_id_gen.get_max_token()
+        result = self._account_data_id_gen.get_current_token()
         defer.returnValue(result)
 
     @defer.inlineCallbacks
@@ -222,7 +222,7 @@ class TagsStore(SQLBaseStore):
 
         self.get_tags_for_user.invalidate((user_id,))
 
-        result = self._account_data_id_gen.get_max_token()
+        result = self._account_data_id_gen.get_current_token()
         defer.returnValue(result)
 
     def _update_revision_txn(self, txn, user_id, room_id, next_id):
diff --git a/synapse/storage/util/id_generators.py b/synapse/storage/util/id_generators.py
index a02dfc7d58..f69f1cdad4 100644
--- a/synapse/storage/util/id_generators.py
+++ b/synapse/storage/util/id_generators.py
@@ -21,7 +21,7 @@ import threading
 class IdGenerator(object):
     def __init__(self, db_conn, table, column):
         self._lock = threading.Lock()
-        self._next_id = _load_max_id(db_conn, table, column)
+        self._next_id = _load_current_id(db_conn, table, column)
 
     def get_next(self):
         with self._lock:
@@ -29,12 +29,16 @@ class IdGenerator(object):
             return self._next_id
 
 
-def _load_max_id(db_conn, table, column):
+def _load_current_id(db_conn, table, column, step=1):
     cur = db_conn.cursor()
-    cur.execute("SELECT MAX(%s) FROM %s" % (column, table,))
+    if step == 1:
+        cur.execute("SELECT MAX(%s) FROM %s" % (column, table,))
+    else:
+        cur.execute("SELECT MIN(%s) FROM %s" % (column, table,))
     val, = cur.fetchone()
     cur.close()
-    return int(val) if val else 1
+    current_id = int(val) if val else step
+    return (max if step > 0 else min)(current_id, step)
 
 
 class StreamIdGenerator(object):
@@ -45,17 +49,32 @@ class StreamIdGenerator(object):
     all ids less than or equal to it have completed. This handles the fact that
     persistence of events can complete out of order.
 
+    Args:
+        db_conn(connection):  A database connection to use to fetch the
+            initial value of the generator from.
+        table(str): A database table to read the initial value of the id
+            generator from.
+        column(str): The column of the database table to read the initial
+            value from the id generator from.
+        extra_tables(list): List of pairs of database tables and columns to
+            use to source the initial value of the generator from. The value
+            with the largest magnitude is used.
+        step(int): which direction the stream ids grow in. +1 to grow
+            upwards, -1 to grow downwards.
+
     Usage:
         with stream_id_gen.get_next() as stream_id:
             # ... persist event ...
     """
-    def __init__(self, db_conn, table, column, extra_tables=[]):
+    def __init__(self, db_conn, table, column, extra_tables=[], step=1):
+        assert step != 0
         self._lock = threading.Lock()
-        self._current_max = _load_max_id(db_conn, table, column)
+        self._step = step
+        self._current = _load_current_id(db_conn, table, column, step)
         for table, column in extra_tables:
-            self._current_max = max(
-                self._current_max,
-                _load_max_id(db_conn, table, column)
+            self._current = (max if step > 0 else min)(
+                self._current,
+                _load_current_id(db_conn, table, column, step)
             )
         self._unfinished_ids = deque()
 
@@ -66,8 +85,8 @@ class StreamIdGenerator(object):
                 # ... persist event ...
         """
         with self._lock:
-            self._current_max += 1
-            next_id = self._current_max
+            self._current += self._step
+            next_id = self._current
 
             self._unfinished_ids.append(next_id)
 
@@ -88,8 +107,12 @@ class StreamIdGenerator(object):
                 # ... persist events ...
         """
         with self._lock:
-            next_ids = range(self._current_max + 1, self._current_max + n + 1)
-            self._current_max += n
+            next_ids = range(
+                self._current + self._step,
+                self._current + self._step * (n + 1),
+                self._step
+            )
+            self._current += n
 
             for next_id in next_ids:
                 self._unfinished_ids.append(next_id)
@@ -105,15 +128,15 @@ class StreamIdGenerator(object):
 
         return manager()
 
-    def get_max_token(self):
+    def get_current_token(self):
         """Returns the maximum stream id such that all stream ids less than or
         equal to it have been successfully persisted.
         """
         with self._lock:
             if self._unfinished_ids:
-                return self._unfinished_ids[0] - 1
+                return self._unfinished_ids[0] - self._step
 
-            return self._current_max
+            return self._current
 
 
 class ChainedIdGenerator(object):
@@ -125,7 +148,7 @@ class ChainedIdGenerator(object):
     def __init__(self, chained_generator, db_conn, table, column):
         self.chained_generator = chained_generator
         self._lock = threading.Lock()
-        self._current_max = _load_max_id(db_conn, table, column)
+        self._current_max = _load_current_id(db_conn, table, column)
         self._unfinished_ids = deque()
 
     def get_next(self):
@@ -137,7 +160,7 @@ class ChainedIdGenerator(object):
         with self._lock:
             self._current_max += 1
             next_id = self._current_max
-            chained_id = self.chained_generator.get_max_token()
+            chained_id = self.chained_generator.get_current_token()
 
             self._unfinished_ids.append((next_id, chained_id))
 
@@ -151,7 +174,7 @@ class ChainedIdGenerator(object):
 
         return manager()
 
-    def get_max_token(self):
+    def get_current_token(self):
         """Returns the maximum stream id such that all stream ids less than or
         equal to it have been successfully persisted.
         """
@@ -160,4 +183,4 @@ class ChainedIdGenerator(object):
                 stream_id, chained_id = self._unfinished_ids[0]
                 return (stream_id - 1, chained_id)
 
-            return (self._current_max, self.chained_generator.get_max_token())
+            return (self._current_max, self.chained_generator.get_current_token())
diff --git a/synapse/util/async.py b/synapse/util/async.py
index 640fae3890..cd4d90f3cf 100644
--- a/synapse/util/async.py
+++ b/synapse/util/async.py
@@ -16,7 +16,8 @@
 
 from twisted.internet import defer, reactor
 
-from .logcontext import PreserveLoggingContext
+from .logcontext import PreserveLoggingContext, preserve_fn
+from synapse.util import unwrapFirstError
 
 
 @defer.inlineCallbacks
@@ -107,3 +108,32 @@ class ObservableDeferred(object):
         return "<ObservableDeferred object at %s, result=%r, _deferred=%r>" % (
             id(self), self._result, self._deferred,
         )
+
+
+def concurrently_execute(func, args, limit):
+    """Executes the function with each argument conncurrently while limiting
+    the number of concurrent executions.
+
+    Args:
+        func (func): Function to execute, should return a deferred.
+        args (list): List of arguments to pass to func, each invocation of func
+            gets a signle argument.
+        limit (int): Maximum number of conccurent executions.
+
+    Returns:
+        deferred: Resolved when all function invocations have finished.
+    """
+    it = iter(args)
+
+    @defer.inlineCallbacks
+    def _concurrently_execute_inner():
+        try:
+            while True:
+                yield func(it.next())
+        except StopIteration:
+            pass
+
+    return defer.gatherResults([
+        preserve_fn(_concurrently_execute_inner)()
+        for _ in xrange(limit)
+    ], consumeErrors=True).addErrback(unwrapFirstError)
diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index 35544b19fd..758f5982b0 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -167,7 +167,8 @@ class CacheDescriptor(object):
                 % (orig.__name__,)
             )
 
-        self.cache = Cache(
+    def __get__(self, obj, objtype=None):
+        cache = Cache(
             name=self.orig.__name__,
             max_entries=self.max_entries,
             keylen=self.num_args,
@@ -175,14 +176,12 @@ class CacheDescriptor(object):
             tree=self.tree,
         )
 
-    def __get__(self, obj, objtype=None):
-
         @functools.wraps(self.orig)
         def wrapped(*args, **kwargs):
             arg_dict = inspect.getcallargs(self.orig, obj, *args, **kwargs)
             cache_key = tuple(arg_dict[arg_nm] for arg_nm in self.arg_names)
             try:
-                cached_result_d = self.cache.get(cache_key)
+                cached_result_d = cache.get(cache_key)
 
                 observer = cached_result_d.observe()
                 if DEBUG_CACHES:
@@ -204,7 +203,7 @@ class CacheDescriptor(object):
                 # Get the sequence number of the cache before reading from the
                 # database so that we can tell if the cache is invalidated
                 # while the SELECT is executing (SYN-369)
-                sequence = self.cache.sequence
+                sequence = cache.sequence
 
                 ret = defer.maybeDeferred(
                     preserve_context_over_fn,
@@ -213,20 +212,21 @@ class CacheDescriptor(object):
                 )
 
                 def onErr(f):
-                    self.cache.invalidate(cache_key)
+                    cache.invalidate(cache_key)
                     return f
 
                 ret.addErrback(onErr)
 
                 ret = ObservableDeferred(ret, consumeErrors=True)
-                self.cache.update(sequence, cache_key, ret)
+                cache.update(sequence, cache_key, ret)
 
                 return preserve_context_over_deferred(ret.observe())
 
-        wrapped.invalidate = self.cache.invalidate
-        wrapped.invalidate_all = self.cache.invalidate_all
-        wrapped.invalidate_many = self.cache.invalidate_many
-        wrapped.prefill = self.cache.prefill
+        wrapped.invalidate = cache.invalidate
+        wrapped.invalidate_all = cache.invalidate_all
+        wrapped.invalidate_many = cache.invalidate_many
+        wrapped.prefill = cache.prefill
+        wrapped.cache = cache
 
         obj.__dict__[self.orig.__name__] = wrapped
 
@@ -240,11 +240,12 @@ class CacheListDescriptor(object):
     the list of missing keys to the wrapped fucntion.
     """
 
-    def __init__(self, orig, cache, list_name, num_args=1, inlineCallbacks=False):
+    def __init__(self, orig, cached_method_name, list_name, num_args=1,
+                 inlineCallbacks=False):
         """
         Args:
             orig (function)
-            cache (Cache)
+            method_name (str); The name of the chached method.
             list_name (str): Name of the argument which is the bulk lookup list
             num_args (int)
             inlineCallbacks (bool): Whether orig is a generator that should
@@ -263,7 +264,7 @@ class CacheListDescriptor(object):
         self.arg_names = inspect.getargspec(orig).args[1:num_args + 1]
         self.list_pos = self.arg_names.index(self.list_name)
 
-        self.cache = cache
+        self.cached_method_name = cached_method_name
 
         self.sentinel = object()
 
@@ -277,11 +278,13 @@ class CacheListDescriptor(object):
         if self.list_name not in self.arg_names:
             raise Exception(
                 "Couldn't see arguments %r for %r."
-                % (self.list_name, cache.name,)
+                % (self.list_name, cached_method_name,)
             )
 
     def __get__(self, obj, objtype=None):
 
+        cache = getattr(obj, self.cached_method_name).cache
+
         @functools.wraps(self.orig)
         def wrapped(*args, **kwargs):
             arg_dict = inspect.getcallargs(self.orig, obj, *args, **kwargs)
@@ -297,14 +300,14 @@ class CacheListDescriptor(object):
                 key[self.list_pos] = arg
 
                 try:
-                    res = self.cache.get(tuple(key)).observe()
+                    res = cache.get(tuple(key)).observe()
                     res.addCallback(lambda r, arg: (arg, r), arg)
                     cached[arg] = res
                 except KeyError:
                     missing.append(arg)
 
             if missing:
-                sequence = self.cache.sequence
+                sequence = cache.sequence
                 args_to_call = dict(arg_dict)
                 args_to_call[self.list_name] = missing
 
@@ -327,10 +330,10 @@ class CacheListDescriptor(object):
 
                     key = list(keyargs)
                     key[self.list_pos] = arg
-                    self.cache.update(sequence, tuple(key), observer)
+                    cache.update(sequence, tuple(key), observer)
 
                     def invalidate(f, key):
-                        self.cache.invalidate(key)
+                        cache.invalidate(key)
                         return f
                     observer.addErrback(invalidate, tuple(key))
 
@@ -370,7 +373,7 @@ def cachedInlineCallbacks(max_entries=1000, num_args=1, lru=False, tree=False):
     )
 
 
-def cachedList(cache, list_name, num_args=1, inlineCallbacks=False):
+def cachedList(cached_method_name, list_name, num_args=1, inlineCallbacks=False):
     """Creates a descriptor that wraps a function in a `CacheListDescriptor`.
 
     Used to do batch lookups for an already created cache. A single argument
@@ -400,7 +403,7 @@ def cachedList(cache, list_name, num_args=1, inlineCallbacks=False):
     """
     return lambda orig: CacheListDescriptor(
         orig,
-        cache=cache,
+        cached_method_name=cached_method_name,
         list_name=list_name,
         num_args=num_args,
         inlineCallbacks=inlineCallbacks,