What do you know about client-server architecture?

Client-server architecture is a model of interaction between processes where one process (client) requests services from another process (server).

Main components:

• Client: The process that initiates the request. This can be a web browser, mobile application, or other software.
• Server: The process that provides services. It receives requests from clients, processes them, and sends responses.

Principles:

• Role separation: Clear division of functions between client and server.
• Request-Response: Interaction occurs on the principle "request from client, response from server".
• Loose coupling: Client and server can be developed and scaled independently, adhering to a certain interaction protocol.

Types of architecture:

• Two-tier: The client interacts directly with the server.
• Three-tier: Includes an additional layer (e.g., application server) that handles business logic between the client and the database server.

Advantages:

• Centralized management of data and resources.
• Higher performance (due to load distribution).
• Improved scalability.
• Simplified maintenance and updates.

Disadvantages:

• Dependence on server availability.
• Complexity in developing and debugging distributed systems.
• Server load with a large number of clients.

Application examples:

• Web applications
• Mobile applications
• Email services
• Banking systems
• Gaming servers

In the context of QA, understanding client-server architecture is critically important for:

• Designing test cases (API testing, server-side performance, client behavior with different server responses).
• Debugging issues (determining where the error occurs - on the client or server).
• Security testing (vulnerabilities at each layer).