Three-Tier Web Architecture

Introduction

For any growing web application, separating responsibilities across frontend, backend, and database layers is a best practice that ensures scalability, flexibility, and maintainability. In this project, I built a production-grade three-tier architecture on AWS that mimics how modern enterprise apps are deployed in the cloud.

The architecture is inspired by a real-world use case I implemented for a mid-size business, helping them move away from a monolithic, single-server deployment to a modular and scalable setup.

Project Goals

• Separate frontend, application logic, and database layers

• Ensure high availability and fault tolerance

• Use scalable AWS services like Auto Scaling and RDS

• Learn and apply security best practices for cloud deployments

• Reflect architecture seen in large-scale production environments

Frontend Layer

For the presentation layer, I deployed a simple static or dynamic web interface (HTML/CSS/JS or PHP) to a fleet of EC2 instances behind an Application Load Balancer (ALB).

• ALB distributes incoming traffic evenly across instances

• Instances are launched in an Auto Scaling Group across multiple Availability Zones

• Apache/Nginx serves the static files or dynamic templates

While in modern systems this could be handled by S3 + CloudFront, I deliberately chose EC2 to simulate a legacy frontend environment common in many business workloads.

Application Layer

The application logic runs on the same EC2 instances in this setup (tightly coupled), but is structured to be abstracted into a dedicated backend tier in future iterations.

• Could support Node.js, Python Flask, or Java Spring apps

• Handles form submissions, API calls, session logic

• Talks directly to the Amazon RDS database using IAM-authenticated connections or credentials stored in EC2 Parameter Store

This design keeps the backend extensible — future improvements could isolate it into containers or Lambda-based microservices.

Database Layer

The data tier is powered by Amazon RDS running MySQL:

• Multi-AZ deployment for high availability

• Automatic backups, snapshots, and failover

• DB subnet group places RDS in private subnets for security

• Connected securely to EC2 via Security Groups and VPC routing

This allowed the business to eliminate self-managed MySQL servers while gaining automated failover, scaling, and monitoring.

Networking & Security

All components are deployed inside a custom VPC with:

• Public subnets for ALB and EC2 instances

• Private subnets for RDS database

• NAT Gateway for EC2 to reach the internet securely (e.g., updates)

• Security Groups:

  • ALB allows inbound HTTP/HTTPS

  • EC2 only accepts traffic from ALB

  • RDS only accepts traffic from EC2

This enforces least-access design and isolates sensitive services.

Monitoring & Logging

To keep tabs on system performance and failures, I integrated:

• Amazon CloudWatch for EC2 metrics, alarms, and custom logs

• ALB access logs to S3

• RDS Enhanced Monitoring for real-time CPU, memory, and connection tracking

These logs can be later extended to build a centralized monitoring dashboard or trigger alerts via SNS.

Infrastructure Deployment

Initial deployment was completed manually through the AWS Console and AWS CLI, which helped build a deeper understanding of resource dependencies. I’m currently migrating this stack to AWS CDK to define:

• VPC architecture

• Auto Scaling Group and ALB

• RDS instance and parameter groups

• Security groups and IAM roles

This transition to IaC ensures repeatability and automated recovery.

Lessons Learned

• Learned to properly segment a VPC using public and private subnets

• Understood ALB listener rules, health checks, and target groups

• Gained experience configuring EC2 scaling policies

• Hardened architecture using Security Groups, IAM roles, and private networking

• Saw firsthand how modular architectures improve operational flexibility
  

Real-World Application

This architecture was modeled after an implementation I designed for a mid-size company transitioning from a single shared server to a layered, cloud-native environment. It enabled them to handle more web traffic, introduce role separation between teams, and prepare for eventual containerization or serverless migration.

Conclusion

Three-tier architecture is a foundational pattern in cloud architecture. It balances separation of concerns, scalability, and control. This project gave me real hands-on experience with AWS compute, networking, database, and security services — all of which are crucial for real-world deployments.

🛠️ Tech Stack:

• Amazon EC2

• Application Load Balancer (ALB)

• Auto Scaling Group

• Amazon RDS (MySQL)

• Amazon VPC

• Amazon CloudWatch

• IAM Roles & Security Groups