I both love and hate CPAN; it has a module for every need, but often, for one reason or another, those modules aren't written by someone who cares about performance.
For example, Crypt::Blowfish is a XS module, which is great, but it's meant to be used, for example, via Crypt::CBC, which is a pure-Perl library, and it runs terribly slow if you encrypt a lot of data (and we do). On the flipside, Crypt::Mode::CBC is a XS module and performs brilliantly (as does the rest of CryptX). Swapping from Crypt::CBC/Crypt::Blowfish to Crypt::Mode::CBC/Crypt::Cipher::Blowfish, we noticed a 7x performance gain in our system.
In the Perl world, when utilising microservices is the right tool for the job, Plack/PSGI is the winning platform for writing RESTful webservices.
An old service that I was maintaining used HTTP::Server::Simple::CGI, which was originally used for the sake of simplicity and getting something up and running with what seemed like a lightweight framework. It was also able to plug in a Net::Server subclass to leverage Net::Server's features, which was desirable from an operational point-of-view given we'd used Net::Server successfully for other purposes. However, HTTP::Server::Simple is terribly written from a performance point-of-view.
Simply porting the service over to Plack/PSGI and serving it out of Starman resulted in a 6x performance gain.
Popular web frameworks, like Mojolicious, support PSGI out of the box, if you'd prefer the abstraction they give you. However, in my experience, even a "Hello World" will run significantly slower. But, depending on the complexity of your service, the performance hit may be worth it.
