Spring Boot consists of different layers and classes to process the data and logic in your backend. The four layers and their use are as follows:

Presentation/display layer: The presentation layer is responsible for interpreting JSON parameters as objects. This layer is the upper layer that is also responsible for handling authentication and HTTP requests. After accomplishing JSON translation and authentication, we will now move to the business layer.

Business layer: The business layer, as the name suggests, handles all the business logic in the application. It is composed of service classes that perform authorization and additional validation.

Persistence layer: The persistence layer is mainly responsible for storage logic that converts objects from and to database rows to insert data.

Database layer: The database layer performs Create, Read, Update, and Delete (CRUD) operations. The layer can consist of multiple databases.