Presence entries are valid for ~10 min (PRESENCE_FRESHNESS_WINDOW_SECONDS in
NestsFeedFilter). Without explicit cleanup, presenceNotes would grow unbounded:
every author who ever heartbeats in a room leaves an entry there forever.
The freshness check kept the filter result correct, but memory only ever grew.
Add LiveActivitiesChannel.pruneStalePresence(cutoff) and call it from
LocalCache.pruneOldMessagesChannel alongside the existing notes prune. Cutoff is
2x the freshness window (20 min) so a presence still inside any feed's window
can never be reaped.
Claude
612f2aa31e