You created your node application, it's ready, you have chosen an 8 vCPU instance to deploy it. You are done with deployment. Everything is working fine, but unknowingly you aren't using the full potential of the deployment. We know that node.js runs on a SINGLE THREAD, which means our node application uses only one vCPU at a time — but you took an 8 vCPU instance, so aren't the other 7 vCPUs sitting there idle?
The solution for this is CLUSTERING. It's a concept of running multiple instances of an application, where each works as an individual entity but still gets the work done and runs on the same port. Now the question is — how will this work? Isn't it going to cause issues among the instances? The simple and short answer is no.
When clustering is done, we end up with multiple processes. There are two kinds:
Primary – There is only one primary. It is responsible for spinning up the worker processes, managing them, and if any one of them dies, spawning it back.
The primary is there only to manage — it doesn't run the code (connecting with db, spinning up server, etc.)
