Something you will notice after working with a Rails application for any amount of time is that it’s easy for your models to get bloated with business logic. ActiveRecord makes it very easy to chuck in non-essential model ideas, such as complex model validation and callbacks. For a small Rails project this isn’t a problem; however, as it begins to grow and your models need to change in the context you’re using them this is when you run into problems.

More often than not when you get to this point you have to start un-winding all of the logic that you have baked into your models. A popular pattern that helps avoid this from happening is the repository pattern, and a great gem for this is rom. At the heart what you get is ActiveRecord, but with forced separation of concerns.

The Pros

• higher uncoupled code
• more supported stores
• easier to test (also faster normally)

The Cons

• larger file code base
• more on-boarding for new developers