I can not post the source code because it’s protected by my employer. You can think about business layer as worflow orchestrator. It calls services from the service layer. Every service has one clear task (probably a group of similar tasks). What the business layer does — it invokes e.g. a method from the service A, then passes the result into a method from the service B, doing some if / else logic, calculations, and similar. It also provides data (as observable RxJS streams) to the facade / presentation layer(s).