Status: IN
Both news feed and chat make irrevocable routing decisions at write time — selecting push vs pull strategy and routing to inbox vs offline queue respectively — with no mechanism to retroactively re-route messages when conditions change.
news feed selects fan-out-on-write vs fan-out-on-read based on follower count at publish time; chat routes to inbox or offline queue based on presence at send time — both decisions are baked in at write time and not revisited
Depends on (SL): news-feed-celebrity-threshold-at-write-time, chat-fanout-on-write