Tell me about three-tier client-server architecture (3-Tier).

The three-tier architecture divides the application into three logical and physical layers:

1. Presentation Tier:
   • User interface (UI).
   • Interacts directly with the user.
   • Sends requests to the application layer and receives data for display.
   • Examples: web browser, mobile application.
2. Application / Business Logic Tier:
   • Contains the application's business logic.
   • Accepts requests from the presentation layer, processes them.
   • Interacts with the data layer to retrieve and store information.
   • Examples: application server, API.
3. Data Tier:
   • Data storage (database, files, etc.).
   • Responsible for storing, retrieving, and managing data.
   • The application layer accesses this layer, but the presentation layer does not have direct access to data.
   • Examples: SQL Server, MySQL, Oracle.

Advantages:

• Separation of concerns: Clear separation of logic makes the code more manageable.
• Scalability: Each layer can be scaled independently.
• Development convenience: Allows different teams to work on different layers in parallel.
• Testing convenience: Layers can be tested in isolation.
• Technology flexibility: Different technologies can be used for different layers.