Backend:
- Atomic seq assignment via Redis Lua script: INCR + GET run atomically
inside a Lua script, preventing duplicate seqs under concurrent requests.
DB reconciliation only triggers on cross-server handoff (rare path).
- Broadcast channel capacity: 10,000 → 100,000 to prevent message drops
under high-throughput rooms.
Frontend:
- Optimistic sendMessage: adds message to UI immediately (marked
isOptimistic=true) so user sees it instantly. Replaces with
server-confirmed message on success, marks as isOptimisticError on
failure. Fire-and-forget to IndexedDB for persistence.
- Seq-based dedup in onRoomMessage: replaces optimistic message by
matching seq, preventing duplicates when WS arrives before REST confirm.
- Reconnect jitter: replaced deterministic backoff with full jitter
(random within backoff window), preventing thundering herd on server
restart.
- Visual WS status dot in room header: green=connected, amber
(pulsing)=connecting, red=error/disconnected.
- isPending check extended to cover both old 'temp-' prefix and new
isOptimistic flag, showing 'Sending...' / 'Failed' badges.
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