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websockets
real-time
system-design
networking

Scaling WebSockets: Sticky Sessions, Fan-Out & Backpressure

11 questions

Running real-time WebSockets across a fleet: why connections need sticky sessions, how a pub/sub backplane fans messages across nodes, tracking presence, per-connection backpressure with bufferedAmount, reconnect storms, and the file-descriptor ceiling. The fan-out math is verified in Node.