Non-blocking Mojolicious applications have the potential to scale to thousands of concurrent connections.

However, most operating systems are not configured to handle that sort of work out-of-the-box. This page details some of the tweaks your server will likely need before it can successfully handle very high concurrent loads. Note that if any part of your application blocks, much of this advice is premature optimization or even irrelevant.
Disclaimer

These tuning parameters are not a substitute for a sane load balancing scheme: they will help get the most out of a single server, but any single machine can and will fall over eventually. One benefit of Mojolicious/hypnotoad is that the multi-process model encourages an application architecture that can be easily scaled across servers (horizontally), and any serious application deployment should be doing exactly that.

Varnish Cache is a web application accelerator also known as a caching HTTP reverse proxy. You install it in front of any server that speaks HTTP and configure it to cache the contents. Varnish Cache is really, really fast. It typically speeds up delivery with a factor of 300 - 1000x, depending on your architecture.

Performance

Varnish performs really, really well. It is usually bound by the speed of the network, effectively turning performance into a non-issue. We’ve seen Varnish delivering 20 Gbps on regular off-the-shelf hardware.

Flexibility

One of the key features of Varnish Cache, in addition to its performance, is the flexibility of its configuration language, VCL. VCL enables you to write policies on how incoming requests should be handled. In such a policy you can decide what content you want to serve, from where you want to get the content and how the request or response should be altered. And, you can extend Varnish with modules (VMODs).

Dunno why I bookmark this shit, maybe because someday I could need it.

You can use environment variable.
For example:

1) NODE_PORT=3002 pm2 start -I 0 app.js

2) Read value in app:

console.log(process.env.NODE_PORT);

Or, if you are build express app:

1) PORT=3002 pm2 start -I 0 ./bin/www

2) Express load PORT automatically at start application.

Unparalleled insights, in real-time, of everything happening on your Linux systems and applications, with stunning, interactive web dashboards and powerful performance and health alarms.