When Rails Engines Are the Wrong Tool

I have spent the better part of this book making the case for Rails engines. Now I am going to tell you when not to use them. This is not a hedge. It is honesty. Every architectural tool has a cost, and engines are no exception. Using them when they are not warranted creates overhead that slows your team down rather than speeding them up. Knowing when not to reach for an engine is just as important as knowing how to build one.