Building Microservices: Designing Fine-Grained Systems

by Sam Newman

A model I prefer and that I’ve seen work well is to restrict the use of these backends to one specific user interface or application, as we see in Figure 4-10. Figure 4-10. Using dedicated backends for frontends This pattern is sometimes referred to as backends for frontends (BFFs). It allows the team focusing on any given UI to also handle its own server-side components. You can see these backends as parts of the user interface that happen to be embedded in the server. Some types of UI may need a minimal server-side footprint, while others may need a lot more. If you need an API authentication and authorization layer, this can sit between our BFFs and our UIs. We’ll explore this more in Chapter 9. The danger with this approach is the same as with any aggregating layer; it can take on logic it shouldn’t. The business logic for the various capabilities these backends use should stay in the services themselves. These BFFs should only contain behavior specific to delivering a particular user experience.