Load balancer without sticky sessions causes repeated handshake resets

Load balancers without session affinity (sticky sessions) cause Socket.io clients to oscillate between backend servers, triggering repeated handshake resets and connection failures. Enabling session persistence reduced errors to sub-1% in documented cases.

Enable sticky sessions or session affinity on load balancers handling WebSocket traffic. Configure session persistence based on client IP or cookie. For HAProxy use 'balance source' or 'stick-table'. For Nginx use 'ip_hash' or 'hash' directive. Verify session mapping consistency across requests.