There are several options but Puma seems to be the most popular at the moment.

A derivative of Unicorn named Pitchfork is also in the works from Shopify - https://github.com/Shopify/pitchfork

Puma works fine most of the time (config it accordingly of course

No idea what other options are out there though

I've been using Nginx/Passenger:

https://www.phusionpassenger.com/library/deploy/nginx/deploy...

I actually switch from Passenger (to puma

But then I got reverse proxy (caddy) in front

We use Puma in production.