Node.js is single threaded and by default utilizes only one core of the CPU no matter how many cores the CPU has. Of course there are solutions of how to use all the cores but it's not part of this post. Just for the record, there are packages that does this job efficiently. Have a look at this link pm2.keymetrics.io/
Well, what am I trying to solve here? Imagine that you have 2 different endpoints on your application, and one of them needs a lot of processing time. What the problem would be?