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Exploring the 3-Tier Architecture with Azure Resources

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Siddhant Bhattarai
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3 min read

In this blog post, we'll break down the 3-tier architecture represented in the image above. This is a common pattern for building scalable, manageable, and robust cloud-based applications. It involves splitting an application into three logical layers: Presentation Tier, Application Tier, and Database Tier. By leveraging Azure resources, each tier can be independently scaled, secured, and optimized for different workloads.

1. Presentation Tier (Front-End)

This layer is responsible for interacting with users, capturing their input, and displaying data. The components in this tier include:

  • Users: Users interact with the system through a web browser or mobile app.

  • Azure Front Door: Azure Front Door is used as a global, scalable entry point, offering fast, secure access to the app with features like load balancing, SSL offloading, and acceleration.

  • Web Servers (VMs or Azure App Services): These are the actual servers hosting the front-end code (HTML, JavaScript, etc.). In this diagram, the web servers are represented by Azure App Services.

When a user makes a request, it passes through the Azure Front Door, which ensures that the request is routed to the nearest or healthiest web server, minimizing latency and enhancing performance.

2. Application Tier (Middle Tier)

The application tier handles the core logic and business rules of the application. It serves as a bridge between the user interface and the database, ensuring that user inputs are validated, processed, and passed to the appropriate data storage.

  • Azure API Management: This component manages the interactions between front-end services and backend services. It serves as a secure gateway for APIs, ensuring controlled access, and providing features like throttling and analytics.

  • Application Servers (VMs or Azure Functions): These servers handle the business logic of the application. In a microservices architecture, Azure Functions can be used to encapsulate small, specific pieces of logic, scaling based on demand.

The application tier receives requests from the presentation tier, processes them, and interacts with the database to retrieve or update data. It also applies the necessary business logic before sending responses back to the presentation tier.

3. Database Tier (Back-End)

This layer stores, retrieves, and manages data. The database tier is typically designed for high availability and scalability, ensuring data integrity and security.

  • MySQL Database: In this example, MySQL databases are used for storing data. Azure Database for MySQL provides a fully managed database service with built-in high availability, automated backups, and scaling capabilities.

  • Replication: The diagram also highlights replication for fault tolerance. Data is replicated across multiple instances for redundancy and availability.

The database servers handle all data-related requests from the application tier, ensuring that data is retrieved or updated in a consistent and secure manner.

Load Balancing and Scalability

The architecture is designed for horizontal scalability. Load balancers (represented by the green icons) distribute incoming traffic across multiple web servers or application servers to ensure even load distribution, which prevents any single instance from being overwhelmed. Azure Load Balancer, or Application Gateway, ensures that traffic is intelligently routed based on server health and traffic conditions.

Benefits of This Architecture

  1. Scalability: Each layer can be independently scaled. For instance, you could scale the web servers in response to high traffic without affecting the application or database layers.

  2. Security: By isolating each tier, security measures can be applied to individual layers, minimizing the attack surface.

  3. Fault Tolerance: Replication in the database tier ensures that if one instance fails, another can take over with minimal disruption.

  4. Separation of Concerns: Each layer is responsible for a specific function, making the system easier to maintain and develop.

Conclusion

The 3-tier architecture with Azure resources offers flexibility, security, and scalability for building modern cloud applications. With Azure services like Front Door, API Management, Load Balancer, and managed MySQL databases, you can create a robust architecture that ensures high performance, reliability, and fault tolerance for mission-critical workloads.