It's not quite coupled to the storage, in that you can use a number of different drivers with ActiveRecord for the actual storage portion. But I think you might

It's not quite coupled to the storage, in that you can use a number of different drivers with ActiveRecord for the actual storage portion. But I think you might mean coupling the model so tightly to it's CRUD logic. Inside the application you are actually trying to get all the benefits of having an Active Record model, not all the benefits of having a Car/Cat/Dog model. So you don't actually have a Car model, you have an Active Record model that represents a Car. Thinking about it that way I think sets the right expectations for what you're trying to achieve.