I was following this guide it documents the puma.rb file that is stored inside the app\'s config directory.
The guide is a bit flakey, but here\'s what
If there is an environment defined - which is the case in your example - the configuration file is read from config/puma/[environment].rb and not config/puma.rb.
Just move your config/puma.rb to config/puma/production.rb and it should work.
Read the Puma documentation for more details: Configuration file