# API Streaming Sse Websocket Long Polling

> Choose SSE, WebSocket, or long-polling for realtime API push: directionality, reconnect, auth limits, and when to use 202 jobs instead. Use when designing event feeds, chat, or live updates.

- Skill: `deangrant/api-streaming-sse-websocket-long-polling` (Agent Skill, multi-file: 4 files)
- Install (CLI): `npx skillmds@latest add deangrant/api-streaming-sse-websocket-long-polling`
- Raw SKILL.md: https://api.skillmd.com/api/skills/deangrant/api-streaming-sse-websocket-long-polling/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- Author: deangrant (https://skillmd.com/u/deangrant)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/deangrant/api-streaming-sse-websocket-long-polling

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# Streaming APIs: SSE, WebSocket, Long-Polling

Use this skill for **continuous push**. One-shot slow work → async **202 + job**,
not streaming.

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## 1. Long-polling

Hold GET until data or timeout (~30s); client reconnects. High header overhead;
fallback for restrictive networks / infrequent updates. Client backoff.

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## 2. SSE (one-way)

`Content-Type: text/event-stream`. Browser `EventSource`; auto-reconnect +
`Last-Event-ID`; keep-alive comments; stop with `204`. Cannot set custom
headers — auth via query token or cookie. Prefer HTTP/3; scale with broker
fan-out.

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## 3. WebSocket (duplex)

Upgrade `101`; full-duplex; heartbeats; reconnect+jitter; sticky LB or shared
registry/pub-sub.

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## 4. Selection

| Need | Prefer |
| ---- | ------ |
| One-way server→client | **SSE** |
| Two-way high-frequency | **WebSocket** |
| Restricted networks | Long-poll |
| Minutes-long CRUD | **202 job** |

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## 5. Quick checklist

- [ ] Correct transport for direction/frequency.
- [ ] Reconnect + keep-alive strategy.
- [ ] Auth compatible with EventSource limits if SSE.
- [ ] Fan-out/broker plan at scale.
- [ ] Not using streams for one-shot jobs.

See [reference.md](reference.md) and [examples.md](examples.md).