What is stored in the data layer?

The Data Layer stores and manages the data used in the application. Its main functions:

1. Data Sources:
   • Local: Room Database, SharedPreferences, file system.
   • Remote: REST APIs, GraphQL APIs.
   • Caching.
2. Repositories:
   • Serve as the "single source of truth" for data.
   • Abstract the logic of fetching, storing, and processing data from higher layers (Domain and UI).
   • Define methods for data access, e.g., getUserProfile(), saveUserData(user).
   • Contain business logic related to data (e.g., choosing between local cache and remote source).

The main goal of the data layer is to provide reliable, scalable, and testable access to data, hiding implementation details from other parts of the application.