Design
This layer is responsible for handling incoming API connections and hosting the endpoints, no processing occurs on this layer. When a request is received this layer will call the correct processing function on the service layer. The service layer will return the processed data to the API layer which can use it as a response to the request
This layer is responsible for processing and collating, this is the actual backend where any algorithms or procedures on data occur. It cannot interact with the API or database but can make calls to the data layer and is called by the API layer.
This layer handles database interaction and exposes the database to the Service layer.