Example 16: WebSockets at Scale (Redis backplane)

[patterncatalyst]

Chapter

_docs/16-appendix-c-websockets.md — WebSockets at Scale

Example Path

examples/16-websockets/

What to demonstrate

• WebSocket endpoint with per-pod connection registry
• Redis pub/sub backplane for multi-pod fan-out
• Resume-don't-restart with sequence numbers
• Scale-out without losing messages

Stack

• Infra: Podman — Redis + LGTM
• Language: Python (FastAPI WebSockets + redis-py)
• Priority: Medium
• Depends on: Add Redis to lgtm-podman-stack skill templates #1 (Redis infra)

Deliverables

• compose.yaml (with Redis)
• WebSocket service with Redis backplane
• Client script for testing resume
• README.md
• verify.sh
• Flip chapter footer to verified