How to deal with large rooms. (SPEC-36)

For every user in the room we currently have a dedicated state event for them. For large rooms with many 1000s or more members this becomes less than ideal due to the overhead for both clients and servers.

The protocol itself only requires knowledge of which servers are in the room.

(Imported from https://matrix.org/jira/browse/SPEC-36)

(Reported by @erikjohnston)

Start by reading the SPEC-36 discussion linked in the issue and the Matrix protocol requirements it references. The issue identifies per-user state events and server membership as the relevant protocol areas, but it does not name files, tests, or a concrete acceptance condition; a resolved design and specification update would define done.

Written by the indexing model from the issue text.