Realtime & Streaming APIs
Every subchapter in this chapter, free to read online. Work through them in order, or jump straight to the runtime detail you need.
WebSocket Protocol & Servers
Trace a WebSocket connection from HTTP upgrade through Node's raw socket handoff, frame parsing, masking, ping/pong liveness, compression, and close behavior.
SSE & Long Polling
Implement HTTP-shaped realtime updates with Server-Sent Events, EventSource reconnects, long polling, cursors, and Node response cleanup.
Realtime Backpressure
Design bounded realtime send paths in Node.js: per-connection queues, slow consumers, bufferedAmount guards, drop and coalescing policy, replay, gaps, and broadcast pressure.
Auth, Heartbeats & Presence
How realtime connections carry identity after upgrade, refresh credentials, reconnect, prove liveness, and derive presence while identity architecture stays in its own layer.
Fanout, Rooms & Scaling
Trace one realtime event through room registries, per-connection queues, process boundaries, backplanes, affinity, and shard-level scaling.