Turn off the bits of Rails you don't use - Andy Croll

The Rails Framework consists of multiple subsystems that work together. The names of these systems typically begin with “Action” or “Active” e.g. Active Record, Active Support, Action Pack, etc.You can see the individual component gems as directories in the rails/rails repo on GitHub.There has been a continual process of adding new, useful libraries to Rails ever since its release. For example, the addition of web socket support via Action Cable was a major feature of Rails 5. Despite the addition of large new sub-frameworks there remains a focus on modularity since Merb was merged into Rails in version 3. (This was big Ruby news at the time!).