Before we start with framework I would like that you understand what is Node.js Cluster. Of cause the best place to get started is official Node.js documentation. But I know that almost no one is gonna read it properly, so this is main part:

A single instance of Node.js runs in a single thread. To take advantage of multi-core systems the user will sometimes want to launch a cluster of Node.js processes to handle the load. The cluster module allows easy creation of child processes that all share server ports. FROM. Also Node.js processes you can call Workers.

In couple of words it is just : “boost your Node.js app by utilizing all cores of your server computer”.

I hope you understand why Node.js Cluster is awesome :) Next is going WebSocket.