Socket.IO Redis Adapter

Socket.IO Redis Adapter is the official Redis-backed adapter for scaling Socket.IO applications across multiple Node.js server instances. It allows events emitted on one Socket.IO server to be broadcast to clients connected to other servers. The adapter uses Redis Pub/Sub as its communication layer, so Socket.IO packets can move between processes without storing persistent session data in Redis. It is useful when an application runs behind a load balancer, in a cluster, or across multiple machines. Developers can use it for chat systems, dashboards, multiplayer apps, notifications, collaborative tools, and any real-time system that needs horizontal scaling. It still requires proper sticky-session configuration at the load balancer level because Socket.IO sessions remain tied to the server that accepted them.