For the past few months at Kiprosh, we've done versions upgrade of multiple mid to large scale Ruby on Rails applications. One of them was running Rails version 3.2.22. That's where we found out that, we need to make a lot of changes in our codebase to run our application on version 4.0. Hence, we thought to write this blog post to share our insights and recommended strategies for upgrading such mid to large Rails applications. upgrading Ruby on RailsRails guides provide us a brief information on how to upgrade the Rails app, but we need to