It's not uncommon to see many frontends that rely on the same backend. Let's say you have a mobile application and a web application, both using the same backend. It may be a good design choice at first. However, once the requirements and usage scenarios of those two applications diverge, your backend will require more and more changes, serving just one of the frontends. This can lead to the backend having to support competing requirements, like two separate ways to update the data store or different scenarios for providing data. Simultaneously, the frontends start to require more bandwidth to communicate with the backend properly, which also leads to more battery usage in mobile apps. At this point, you should consider introducing a separate backend for each frontend.
This way, you can think of a user-facing application as being a single entity having two layers: the frontend and the backend. The backend can depend on another layer, consisting of downstream...
