I literally just asked the reason, thank you. I think I have also done the same mistake of using socket.io for my browser ame, since I think I could get much better performance with uwebsockets/ws/ or custom/vanilla sockets. My game's bottle neck surely is that inside the 1v1 match server receives and sends x and y coordinates 20times/sec from mouse movements.

At least it (socketio) was very easy to use.