https://socket.io/docs/v4/using-multiple-nodes/ https://socket.io/docs/v4/using-multiple-nodes/#why-is-sticky-session-required
you can add a cookie to incoming request here's how you do that for aws loadbalancer
https://socket.io/docs/v4/redis-adapter/ check out the architecture diagram on the page to get a better sense of how clustering could work with socketio.
nodejs has some support for clustering? https://socket.io/docs/v4/using-multiple-nodes/#using-nodejs-cluster