Deploying a Highly Available Three-Tier Architecture in AWS using Terraform

Introduction

When building a cloud-based application, it’s critical to consider the underlying architecture and environment to ensure scalability, availability, and security. Using Infrastructure-as-Code (IaC) tools like Terraform has become increasingly popular for automating the deployment and management of cloud resources.

In this article, we’ll explore how to deploy a highly available three-tier architecture in AWS using Terraform. Our architecture will consist of:

• An EC2 Auto Scaling group for our web tier and app tier

• An RDS MySQL database for our data tier

• A bastion host for secure remote access

Using Terraform enables us to efficiently deploy and manage resources while ensuring our architecture is scalable, highly available, and secure.

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What is Three-Tier Architecture and Why Three-Tier?

A Three-Tier Architecture is a widely used architectural pattern for cloud-based applications. It provides increased scalability, availability, and security by dividing the application into three distinct layers:

1. Web/Presentation Tier (Front End): Houses user-facing elements such as web servers and interfaces.

2. Application Tier (Back End): Manages backend logic and processes user requests.

3. Data Tier: Stores and manages application data, typically in a database.

Benefits of Three-Tier Architecture:

• Scalability: Each tier can scale independently to handle demand.

• Availability: Resources spread across multiple Availability Zones (AZs) ensure resilience.

• Security: Tiers are isolated using security groups and private subnets, reducing attack surfaces.

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Architecture Overview

We will deploy the following components:

Network Infrastructure

• VPC with a CIDR block of 10.0.0.0/16

• Subnets:

  • 2 public subnets for the web tier (10.0.0.0/28, 10.0.0.16/28)

  • 2 private subnets for the application tier (10.0.0.32/28, 10.0.0.48/28)

  • 2 private subnets for the database tier (10.0.0.64/28, 10.0.0.80/28)

• Route Tables:

  • A public route table connected to an Internet Gateway

  • A private route table connected to a NAT Gateway

Compute and Storage

• Web Tier: EC2 Auto Scaling group across public subnets

• App Tier: EC2 Auto Scaling group across private subnets

• Data Tier: RDS MySQL instance deployed across two AZs

Additional Components

• Load Balancers:

  • An Application Load Balancer (ALB) for the web tier

  • An internal ALB for the app tier

• Bastion Host: For secure access to private subnets

• Elastic IPs, Internet Gateway, and NAT Gateway: For connectivity

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Implementation Steps

Prerequisites

• An AWS account with IAM user access

• A code editor (e.g., VS Code)

• Familiarity with Terraform, Linux commands, and SSH

You can find all of the Terraform code used in this tutorial on the following GitHub repository:

https://github.com/rahulwath/Three-Tier-Architecture-Terraform

• Clone this repository to your local machine.

• Install Terraform and configure your AWS credentials.

• Review and update the Terraform configuration files as needed.

• Run terraform init to initialize the Terraform working directory.

• Run terraform apply to deploy the infrastructure.

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Conclusion

Deploying a highly available three-tier architecture using Terraform ensures scalability, availability, and security for your application. By following this guide, you can achieve a robust and efficient infrastructure in AWS that aligns with modern best practices. Terraform’s declarative syntax makes it easier to automate and manage complex environments, allowing you to focus on building your application.