realtime-patterns

Use SSE for one-way server-to-client streams like notifications, live feeds, and AI token streaming since it has built-in auto-reconnection and works through HTTP proxies. Use WebSocket for bidirectional communication like chat, gaming, and collaborative editing.

Wrap the WebSocket in a class that listens for onclose and retries with exponential backoff, capping delay at 30 seconds and limiting max retries. Reset the retry counter on successful connection to avoid permanent backoff after temporary failures.

Run a periodic interval that calls ping() on every open connection, typically every 30 seconds. Clients respond with pong automatically; connections that stop responding can be terminated and removed from the client registry.

Cancel in-flight queries, snapshot the current cache, apply the new state immediately via setQueryData, then roll back to the snapshot in onError. Invalidate the query in onSettled to refetch authoritative server state.

Yes, SSE works through most HTTP proxies and CDNs since it uses standard HTTP. Set the X-Accel-Buffering: no header to disable nginx buffering, and send periodic heartbeat comments to prevent idle connection timeouts.

HTTP polling introduces latency equal to the poll interval and wastes requests when nothing has changed. It is the simplest option and works everywhere, but SSE or WebSocket is preferable for frequent updates.