Large, monolithic applications are hard to maintain and slow to test. That is part of the reason that microservices architectures are becoming more and more popular. Moving to a microservices architecture entails significant refactoring, though, or more up-front design work. When you are not quite ready to transition into the world of microservices, Rails Engines are the way to go.
In this Coffee Break Course, Envato Tuts+ instructor Markus Mühlberger will show you how to use Rails Engines to modularize your app one piece at a time. This will let you test all its components independently and therefore more quickly. You'll also see how you could use Rails Engines to create multiple interfaces with different functionality depending on the app data.