1. Presentation Layer:
   • This layer handles HTTP requests and responses. It consists of REST controllers that manage incoming requests, perform request validation, and serialize/deserialize JSON data. The presentation layer forwards processed requests to the business layer for further processing.
2. Business Layer:
   • The business layer contains the core logic of the application. It consists of service classes that implement business rules, process and validate data, and handle transactions. This layer acts as an intermediary between the presentation and persistence layers, ensuring that the controller does not contain business logic.
3. Persistence Layer:
   • This layer is responsible for data access and management. It includes repository classes that interact with the database using Spring Data JPA or other ORM frameworks. The persistence layer handles CRUD operations and maps Java objects to database records, ensuring that data is stored and retrieved efficiently.
4. Database Layer:
   • The database layer consists of the actual database where application data is stored. It can support various types of databases, including relational databases (like MySQL and PostgreSQL) and NoSQL databases (like MongoDB). This layer is crucial for data persistence and retrieval.

• Separation of Concerns: Each layer has a specific responsibility, making the codebase easier to manage and understand.
• Scalability: The architecture allows for easy expansion of the application by adding new features or layers without affecting existing functionality.
• Maintainability: Changes in one layer (e.g., business logic) do not directly impact other layers, reducing the risk of introducing bugs during updates.

Spring Boot's layered architecture promotes a clean and organized structure for building applications, making it easier for developers to maintain and scale their projects. By understanding the roles of each layer, developers can effectively design and implement robust applications using Spring Boot.This architecture not only simplifies development but also enhances the overall quality and performance of the application. For more detailed information, you can refer to the sources.