Remove mutual_rooms `update_user_directory` check, and add extra documentation (#12038)

Resolves #10339

1 files changed, 10 insertions, 1 deletions

diff --git a/docs/workers.md b/docs/workers.md
index 9eb4194e4d..8ac95e39bb 100644
--- a/docs/workers.md
+++ b/docs/workers.md
@@ -528,10 +528,19 @@ the following regular expressions:
 
     ^/_matrix/client/(r0|v3|unstable)/user_directory/search$
 
-When using this worker you must also set `update_user_directory: False` in the
+When using this worker you must also set `update_user_directory: false` in the
 shared configuration file to stop the main synapse running background
 jobs related to updating the user directory.
 
+Above endpoint is not *required* to be routed to this worker. By default,
+`update_user_directory` is set to `true`, which means the main process
+will handle updates. All workers configured with `client` can handle the above
+endpoint as long as either this worker or the main process are configured to
+handle it, and are online.
+
+If `update_user_directory` is set to `false`, and this worker is not running,
+the above endpoint may give outdated results.
+
 ### `synapse.app.frontend_proxy`
 
 Proxies some frequently-requested client endpoints to add caching and remove