Building a Three-Tier Web Application on AWS - Project #3

Hello Cloud learners,

Hope everyone doing great and upskilling your AWS Cloud computing journey.

I hold few active AWS certifications and would like to showcase my AWS skills by doing hands-on projects. This time it’s interesting and commonly deployed Three tier application architecture using AWS.

Almost all the companies businesses rely on scalable, secure, and highly available infrastructure to support their web applications. Whether you're building an e-commerce platform, a SaaS product, or a dynamic content website, the three-tier web application architecture is a proven design pattern that ensures scalability, resilience, and modularity.

This blog post will guide you through deploying a production-grade three-tier web application on AWS, incorporating load balancing, auto-scaling, and high availability. By the end of this article, you'll have an in-depth understanding of how to leverage AWS services like VPC, EC2, Auto Scaling Groups (ASG), Elastic Load Balancer (ELB), and Amazon RDS to build a robust infrastructure for your application.

What is a Three-Tier Architecture?

A three-tier architecture divides an application into three logical layers:

1. Presentation Layer (Web Tier): This layer handles user interactions and serves static content such as HTML, CSS, and JavaScript. It acts as the entry point for users.

2. Application Layer (App Tier): This layer contains the business logic of the application. It processes user requests and interacts with the database.

3. Data Layer (Database Tier): This layer stores and retrieves data for the application.

Real-World Analogy

Think of a three-tier architecture like a restaurant:

• The Web Tier is like the host at the front desk who greets customers and takes their orders.

• The App Tier is the chef in the kitchen who prepares meals based on those orders.

• The Database Tier is the pantry where all the ingredients are stored.

By separating these responsibilities into distinct layers, you can scale each tier independently based on demand while maintaining security and performance.

Why Choose AWS for a Three-Tier Architecture?

AWS provides a rich ecosystem of services that make it easy to build scalable, secure, and highly available applications. Here are some reasons why AWS is ideal for deploying a three-tier web application:

1. Scalability: Services like Auto Scaling Groups (ASG) ensure your application can handle traffic spikes by dynamically adding or removing resources.

2. High Availability: Multi-AZ deployments and load balancers ensure your application remains available even during failures.

3. Security: AWS offers fine-grained control over network access with Security Groups, Network ACLs, and AWS WAF.

4. Cost Optimization: Pay-as-you-go pricing models and tools like Cost Explorer help you optimize costs.

Architecture Overview

Here is the architecture diagram:

Key Components

1. Virtual Private Cloud (VPC): A private network where all resources are deployed.

2. Elastic Load Balancer (ELB): Distributes incoming traffic across multiple servers to ensure no single server is overwhelmed.

3. Auto Scaling Groups (ASG): Automatically adjusts the number of EC2 instances based on traffic patterns.

4. Amazon RDS: A managed relational database service for storing application data.

Step 1: Setting Up the VPC

A Virtual Private Cloud (VPC) is your private network within AWS where you deploy all your resources.

Components of VPC

1. Subnets:

   • Public Subnets: Host resources that need internet access (e.g., load balancers).

   • Private Subnets: Host resources that should remain isolated (e.g., app servers and databases).

2. Internet Gateway: Allows public subnets to connect to the internet.

3. NAT Gateway: Enables private subnets to access the internet without exposing them directly.

4. Route Tables: Define how traffic flows within your VPC.

Real-World Analogy

Think of a VPC as a gated community:

• Public subnets are like common areas accessible to visitors.

• Private subnets are like individual homes accessible only to residents.

Implementation Steps

1. Create a VPC with CIDR block 10.0.0.0/16.

2. Divide it into subnets across multiple Availability Zones:

   • Public Subnet 1: 10.0.1.0/24

   • Public Subnet 2: 10.0.2.0/24

   • Private Subnet 1: 10.0.3.0/24

   • Private Subnet 2: 10.0.4.0/24

3. Attach an Internet Gateway to the VPC.

4. Create route tables for public and private subnets.

Step 2: Deploying Elastic Load Balancers

Elastic Load Balancers distribute incoming traffic across multiple EC2 instances to ensure no single instance becomes overwhelmed.

Types of Load Balancers

1. Internet-facing ALB: Routes traffic from users to the web tier.

2. Internal ALB: Routes traffic from the web tier to the app tier.

Real-World Analogy

Think of load balancers as traffic cops directing cars to open lanes during rush hour.

Implementation Steps

1. Create an Internet-facing Application Load Balancer in public subnets.

2. Configure target groups for EC2 instances in the web tier.

3. Set up an Internal ALB in private subnets for app tier communication.

Step 3: Configuring Auto Scaling Groups

Auto Scaling Groups ensure your application can handle varying levels of traffic by automatically adding or removing EC2 instances based on demand.

Key Features

1. Dynamic Scaling: Adjusts capacity based on metrics like CPU utilization or request count.

2. Scheduled Scaling: Prepares for predictable traffic patterns (e.g., morning login rush).

Real-World Example

Imagine running a coffee shop that hires extra baristas during peak hours and sends them home during slow periods.

Implementation Steps

1. Create Launch Templates for EC2 instances in both tiers:

   • Web Tier: Use Amazon Linux AMI with NGINX installed.

   • App Tier: Use Amazon Linux AMI with your business logic deployed.

2. Configure Auto Scaling Policies:

   • Scale out when CPU utilization exceeds 70%.

   • Scale in when CPU utilization drops below 30%.

Step 4: Setting Up Amazon RDS

Amazon RDS provides managed relational databases with built-in high availability features like Multi-AZ deployments.

Key Features

1. Multi-AZ Deployment: Ensures failover protection by replicating data across Availability Zones.

2. Read Replicas: Improves performance by offloading read queries from the primary database.

Real-World Analogy

Think of RDS as a library with multiple copies of popular books available in different branches for redundancy.

Implementation Steps

1. Launch an RDS instance using MySQL or PostgreSQL.

2. Enable Multi-AZ deployment for high availability.

3. Restrict access to only allow connections from app servers in private subnets.

Step 5: Security Best Practices

Security is critical when deploying production-grade applications on AWS.

Key Measures

1. Security Groups:

   • Web Tier: Allow HTTP/HTTPS traffic from anywhere and SSH only from trusted IPs.

   • App Tier: Allow traffic only from the web tier’s security group.

   • Database Tier: Allow traffic only from the app tier’s security group.

2. Network ACLs:

   • Block malicious IPs at the subnet level.

3. AWS WAF:

   • Protect against common attacks like SQL injection and Cross-Site Scripting (XSS).

Step 6: Cost Optimization

AWS provides several tools to help you optimize costs while maintaining performance:

1. Use Spot Instances for stateless workloads in the app tier.

2. Right-size EC2 instances based on CloudWatch metrics.

3. Reserve capacity for long-term database workloads using Reserved Instances.

Monitoring & Maintenance

Monitoring your infrastructure ensures smooth operation:

1. Use Amazon CloudWatch to track metrics like CPU utilization and request count.

2. Set up alarms to notify you of unusual activity or resource failures.

3. Automate backups using RDS snapshots and S3 versioning.

Conclusion

Deploying a three-tier web application on AWS allows you to build scalable, secure, and highly available systems tailored to modern business needs. By leveraging services like VPC, ELB, ASG, and RDS, you can create an infrastructure that grows with your user base while minimizing downtime and optimizing costs.

Whether you're running an e-commerce store or launching a SaaS platform, this architecture provides a solid foundation for success in the cloud era.

This comprehensive guide covered every aspect of designing and deploying a production-grade three-tier web application on AWS in detail while ensuring simplicity through analogies and real-world examples tailored to both beginners and seasoned professionals alike!

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Cheers,

Logeswaran GV