Building microservices has always been a good enterprise solution to break down monolithic applications into functional components that can still interact with each other at runtime, yet have no dependencies on each other when it comes to scalability and code maintenance. Since the first chapter, this book has been using the hrs databases consisting of three domain scopes in one application: the login, the employee, and the department domains. It has reached this point where we design and build each domain its own Spring Boot application which caters all the request-response transactions through RESTful services only within the bound of its domain's details.

From the previous huge application, the completion of this recipe will lead us to three applications that depict three service boxes that run side-by-side that can cater the same as the typical single HR application but with more manageable components. This kind of architecture cannot be possible without the use of @RestController and its related annotations to expose services that can respond to all user requests to transact with the hr data source.

But what is unique with this recipe is the clear proof that the Spring 5 web and functional framework has strong support not only for the usual blocking services, but also for the asynchronous and reactive RESTful service implementation. It gives us an approach to build a service box that can contain any of these types or all of them to satisfy client requirement. Spring Boot 2.0 has provided us the easiest and most straightforward methodology for building reactive microservices. The following diagram will summarize the three microservices after this recipe: