2 files changed, 6 insertions, 4 deletions
diff --git a/changelog.d/17632.misc b/changelog.d/17632.misc
new file mode 100644
index 0000000000..756918e2b2
--- /dev/null
+++ b/changelog.d/17632.misc
@@ -0,0 +1 @@
+Pre-populate room data used in experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint for quick filtering/sorting.
diff --git a/synapse/storage/databases/main/events_bg_updates.py b/synapse/storage/databases/main/events_bg_updates.py
index 3160e12bb3..b86f873eba 100644
--- a/synapse/storage/databases/main/events_bg_updates.py
+++ b/synapse/storage/databases/main/events_bg_updates.py
@@ -1967,12 +1967,13 @@ class EventsBackgroundUpdatesStore(StreamWorkerStore, StateDeltasStore, SQLBaseS
             txn.execute(
                 """
                 SELECT event_id, membership
-                FROM room_memberships
+                FROM room_memberships AS m
+                INNER JOIN events AS e USING (room_id, event_id)
                 WHERE
                     room_id = ?
-                    AND user_id = ?
-                    AND event_stream_ordering < ?
-                ORDER BY event_stream_ordering DESC
+                    AND m.user_id = ?
+                    AND e.stream_ordering < ?
+                ORDER BY e.stream_ordering DESC
                 LIMIT 1
                 """,
                 (