I used pow in the past and didn't like it. I've given it a second chance and it seems to be working out. I'd like to give Invoker a try though but I'll save that for another day.
Pow is a daemon that runs your rack (Rails) apps in the background when you request them at a special
example_app.dev domain. You don't have to start your app manually anymore (e.g.
rails s). If you don't use your app for 15 minutes it kills your app's process to free up memory (restarting it on the next request). It doesn't run workers (I recommend inline que workers via ActiveJob) or other daemons such as those in your
Procfile. It just looks for a
config.ru and (presumably) does a
rackup on it. It's very simple to set up and it's Mac OS X only.