WebSocket & Real-Time Patterns

Complete WebSocket and real-time communication patterns for Node.js, Python, and Go. Every production app eventually needs server-push — chat, notifications, live dashboards, collaborative editing. This skill covers the hard parts that tutorials skip: connection lifecycle management with heartbeats and dead connection cleanup, client reconnection with exponential backoff and message buffering, three authentication strategies (query string, first-message, cookie-based), scaling across multiple servers with Redis pub/sub, room and channel management, presence tracking with typing indicators, message protocol design with acknowledgments, rate limiting per-connection, nginx load balancing config for WebSocket upgrade, and complete architectures for chat, dashboards, notifications, and collaborative editing. Includes 16KB of production-ready code patterns, performance checklist, close code reference, and load testing setup with Artillery. Whether you are using raw ws, Socket.IO, or SSE, this skill tells you which to pick and how to implement it correctly.