API Style & Pattern Comparisons
Side-by-side trade-offs. Neither column wins — the consumer environment, the data shape and the operational budget decide.
WebSockets vs Server-Sent Events
A bidirectional message channel you design a protocol for vs one-way server-to-client streaming that stays plain HTTP — reconnect logic included.
The client talks back at conversation speed: chat, collaborative editing, multiplayer state, live bidding.
Updates flow one way and a POST covers the rare upstream message — you're paying protocol-design cost for nothing.
Full duplex, low per-message overhead, one connection for the whole conversation.
You skip the boring parts — reconnect, resubscription, message ordering, schema evolution — and every client reinvents them badly.
Stateful connections to drain on deploy, heartbeats, an in-house message contract to version, WS-aware infrastructure.
The server pushes and the client mostly listens: notifications, progress updates, dashboards, AI token streams.
The client must send frequent low-latency messages upstream — pairing SSE with POSTs gets clumsy past a point.
Plain HTTP: works through proxies and LBs, auto-reconnect with Last-Event-ID resume built into the browser.
You need client→server flow beyond occasional requests, or must push binary frames.
Long-lived HTTP connections to budget for; event-id bookkeeping so resume actually replays missed events.
| Dimension | WebSockets | Server-Sent Events |
|---|---|---|
| Direction | Bidirectional | Server → client only |
| Protocol | Upgraded connection; your own message contract on top | Plain HTTP response that never ends |
| Reconnect & resume | Yours to design: detect, reconnect, resubscribe, replay | Browser reconnects automatically; Last-Event-ID resumes the stream |
| Infrastructure fit | Needs WS-aware proxies, LBs and timeouts | Anything that streams HTTP responses works |
| Payload types | Text and binary frames | UTF-8 text events only |