If you're following the guidelines of the Service layer when defining your classes, methods, parameters, and interfaces (as discussed later in this chapter), then any API based on this layer should already mirror the functional terms used in your application. Having a good alignment with your application terms makes your API easier to map to functional concepts in your application and thus for Developer X to navigate around, understand, and discuss with those that know the application in more functional depth.

In addition, like the Service layer, your API should support platform concerns such as bulkification and not prevent Developer X from calling your API in a bulkified way to make optimal use of the platform resources. This also includes Developer X utilizing Apex DML statements, and thus raises the importance of bulkified Domain layer logic as well as bulkified Service layer logic.