Real-Time Systems

Design WebSocket, push, polling, and streaming systems with predictable fanout.

35 min

3 sections

websocket

realtime

fanout

01. Pick the right delivery model

Section 1 of 3

Polling is simple and reliable. Server-sent events are good for one-way streams. WebSockets are good for bidirectional sessions. Push notifications are good for offline mobile users but have provider limits and delivery uncertainty.

text

Delivery model examples:
- Order status page: polling or SSE.
- Collaborative document: WebSocket.
- Trading quote feed: WebSocket or specialized stream.
- Marketing notification: mobile push plus email fallback.
- Typing indicator: WebSocket, best-effort delivery.

Search and Read Models

Idempotency, Sagas, and Recovery

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