What is the difference between four 1X dynos and two 2X dynos in heroku?
heroku
Solution
More dynos give you more concurrency. Based on a single threaded web server such as thin, if you have 4 x 1x dynos, you can serve four requests at the same time.
With 2 x 2x dynos you can only serve two requests.
2x dynos have more memory (1024MB) and more CPU available. This is useful if your application takes up a lot of memory. Most apps should not need 2x dynos.
Heroku have recently added PX dynos as well, which have significantly more power available.
You can read about the different dynos Heroku offers on their website.
Problem
Does anyone know the answer for this? I spawned two 2X dynos on heroku and the performance with the free 1X dyno is much better than the two 2X dynos. They both have the same Rails app talking to the same database. Boggles my mind!