In the most careful WebSockets vs SSE vs long polling benchmark I've found this year, WebSockets won. A raw WebSocket put 119,692 bytes on the wire for 1,000 events, where SSE needed 131,596. On a Node server, each idle WebSocket held about 13 KB of memory and each SSE connection about 23 KB. I'd still pick SSE (server-sent events) for most of the real-time features I see people build with Socket.IO. The numbers are below, along with why I don't think they change the answer and the nginx and ...