A three-tier architecture separates an application into three logical and physical computing layers:
- Presentation Tier (Client Tier): This layer handles the user interface and user interaction. It's what the end-user sees and interacts with, typically a web browser or a desktop application.
- Application Tier (Logic Tier/Middle Tier): This layer contains the business logic, processes, and application services. It acts as an intermediary, receiving requests from the presentation tier, processing them, and interacting with the data tier.
- Data Tier (Database Tier): This layer is responsible for storing and managing the application's data. It typically consists of database servers and associated management systems.
Key design principles include:
- Separation of Concerns: Each tier has a distinct responsibility, making the system easier to develop, manage, and scale.
- Independent Scalability: Each tier can be scaled independently based on its specific load requirements.
- Enhanced Security: Tiers can be placed in different network segments, with firewalls controlling communication, limiting direct access to the data tier.
- Technology Flexibility: Different technologies can be used for each tier, allowing for optimal choices for specific functions.
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