The question behind the term
A websocket can deliver the next event quickly while a reconnecting client silently misses the previous ten. Realtime correctness requires a durable ordering contract outside the live connection.
A reviewable approach
Commit authoritative state and a recipient-visible sequence atomically. Clients keep a durable cursor, recover the exact interval after reconnect and use stable operation IDs so optimistic retries do not duplicate work.
- Name the source of truth
- Commit change and recovery cursor together
- Make retries idempotent
- Test gaps, duplicates, reordering and resets
The boundary to keep visible
Ordering guarantees must name their scope. A per-user sequence can order account changes without globally ordering every event, and presence remains an ephemeral observation rather than durable proof.