What is a two-tier and three-tier architecture? What are the pros and cons?

Two-tier architecture (2-tier) is a model where the client directly interacts with the database server. Typically, the client contains the user interface and business logic, while the server is responsible for data storage and management.

Pros:

• Simplicity of implementation and deployment.
• Fast data exchange between client and server.

Cons:

• Limited scalability.
• Difficulties in maintaining and updating business logic on the client.
• High load on the database server.

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Three-tier architecture (3-tier) divides the system into three layers:

1. Presentation layer — user interface.
2. Application layer — business rules and data processing.
3. Data layer — database management.

Pros:

• Better scalability and flexibility.
• Separation of responsibilities simplifies support and development.
• Ability to independently update each layer.

Cons:

• More complex architecture and setup.
• Potential increase in latency due to an additional layer.

Thus, the choice between two-tier and three-tier architecture depends on requirements for scalability, support, and system complexity.