You can find the full tutorial for adding concurrency to Rails apps on Heroku by checking out the original post. Here's a little more information on what you'll find there:
If you are running Ruby on Rails with Thin, or another single-threaded server, you may be seeing bottlenecks in your application. These servers only process one request at a time and can cause unnecessary queuing. Instead, you can improve performance by choosing a concurrent server such as Unicornwhich will make your app faster and make better use of your system resources. In this article we will explore how Unicorn works, how it gives you more processing power, and how to run it on Heroku.