...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.