Leveraging Terraform for Infrastructure as Code: A Case Study

Terraform as Code AWS DigitalCloudAdvisor

At DigitalCloudAdvisor, we harness the power of Terraform, an open-source infrastructure as code (IaC) tool, to assist our clients in automating and managing their infrastructure. Terraform enables us to define and provision data centre infrastructure using a high-level configuration language. This comprehensive case study will delve into how Terraform can be utilised for both simple and complex infrastructures, ensuring efficient, scalable, and repeatable deployments.

Introduction to Infrastructure as Code with Terraform

Infrastructure as Code (IaC) is a methodology that allows developers and operations teams to manage and provision computing infrastructure through machine-readable definition files rather than physical hardware configuration or interactive configuration tools. Terraform, developed by HashiCorp, stands at the forefront of IaC tools, offering a declarative approach to infrastructure management.

Terraform utilises its domain-specific language (DSL) called HashiCorp Configuration Language (HCL), which is designed to be both human-readable and machine-friendly. This language allows users to describe their desired infrastructure state, and Terraform takes care of the rest, determining the necessary steps to achieve that state.

One of the key advantages of using Terraform for infrastructure as code is its provider-agnostic nature. While our case study focuses on AWS, Terraform supports many cloud providers and services, making it a versatile choice for organisations with multi-cloud or hybrid cloud strategies.

Small Infrastructure Example

Terraform streamlines the provisioning and managing of resources for smaller infrastructures, such as a simple web application setup. Let’s explore a practical scenario to illustrate this.


A small business aims to deploy a web application on AWS. The architecture includes an EC2 instance running a web server and an RDS instance for the database. This straightforward setup is an excellent example of how Terraform can simplify infrastructure management even for smaller-scale projects.


Terraform as Code AWS DigitalCloudAdvisor
Terraform as Code on AWS – Small Infrastructure Example

To implement this infrastructure using Terraform, we would create a main.tf file containing the necessary resource definitions. Here’s a simplified example of what this might look like:

provider "aws" {
    region = "eu-west-2"

resource "aws_instance" "web_server" {
    ami = "ami-0e5f882be1900e43b"
    instance_type = "t2.micro"
    tags = {
        Name = "Web Server"
resource "aws_db_instance" "database" {
     engine = "mysql"
     engine_version = "5.7"
     instance_class = "db.t2.micro"
     name = "mydb"
     username = "admin"
     password = "password"

This Terraform configuration defines an EC2 instance for the web server and an RDS instance for the database. With just these few lines of code, we can provision the entire infrastructure for our small business client.

The beauty of using Terraform for such a setup lies in its simplicity and reproducibility. Should the client need to set up a similar environment for testing or development, we can easily reuse this code, making only minor adjustments as necessary.

Complex Architecture Example

While Terraform shines in simple setups, its true power becomes evident when dealing with more extensive, complex infrastructures. Terraform’s modularity and reusability are invaluable for such scenarios.


A large enterprise requires a 3-tier application architecture on AWS, including VPC, multiple subnets, multiple EC2 instances, RDS instances, S3 buckets, Application Load Balancers and Auto Scaling Groups. This complex setup demonstrates how Terraform can manage intricate, interconnected resources effectively.

Solution – Modular Design

For such a complex architecture, we break down the infrastructure into reusable modules. Each module is responsible for a specific part of the infrastructure, such as VPC, compute resources, databases, and serverless functions. This modular approach not only makes the code more manageable but also promotes reusability across different projects or environments.

Terraform as Code AWS DigitalCloudAdvisor
Terraform as Code on AWS – Modular Design Example

Solution – Defining Modules

Each module is defined in a separate directory with its configuration files. For our 3-tier application, we might have the following module structure:

├── main.tf
├── variables.tf
├── outputs.tf
├── modules/
│ ├── vpc/
│ ├── ec2/
│ ├── rds/
│ ├── s3/
│ ├── alb/
│ └── asg/

Each module (vpc, ec2, rds, etc.) would have its main.tf, variables.tf, and outputs.tf files, defining the resources, input variables, and outputs for that specific infrastructure component.

In the root main.tf file, we would then call these modules:

module "vpc" {
     source = "./modules/vpc"
     # ... variable inputs ...

module "ec2" {
     source = "./modules/ec2"
     vpc_id = module.vpc.vpc_id
     # ... other variable inputs ...

# ... other module calls ...

This modular approach allows us to manage complex infrastructures more effectively, reuse components across different projects, and maintain a clear separation of concerns.

Solution – Provisioning and Managing

Using terraform init and terraform apply, we provision the entire infrastructure. Terraform maintains the state, allowing for easy updates and scaling. The state file keeps track of the real-world resources that Terraform manages, enabling it to determine what changes need to be made to the infrastructure when the configuration is updated.

For large-scale infrastructures, we often use remote state storage (such as an S3 bucket) and state locking (using DynamoDB) to enable team collaboration and prevent concurrent modifications:

terraform {
    backend "s3" {
       bucket = "terraform-state-bucket"
       key = "prod/terraform.tfstate"
       region = "eu-west-2"
       dynamodb_table = "terraform-state-lock"

Solution – Compliance and Security

We incorporate security best practices and compliance checks using Terraform. For example, encryption on RDS instances can be enforced, and IAM roles and policies can be implemented. Here’s an example of how we might enforce encryption on an RDS instance:

resource "aws_db_instance" "default" {
       # ... other configurations ...
       storage_encrypted = true
       kms_key_id = aws_kms_key.rds.arn
   resource "aws_kms_key" "rds" {
   description = "KMS key for RDS encryption"


Solution – Automation and Integration

Terraform can be integrated with CI/CD pipelines to automate deployments and infrastructure changes. We automate the application deployment process using tools like Jenkins, GitLab CI, or AWS CodePipeline, ensuring quick and reliable updates.

For instance, in a GitLab CI pipeline, we might have a stage that runs Terraform:

  stage: plan
    - terraform init
    - terraform plan -out=tfplan
      - tfplan
  stage: apply
    - terraform apply -auto-approve tfplan
  when: manual

This setup allows for automated planning of infrastructure changes, with a manual approval step before applying the changes.

Benefits of Using Terraform for Infrastructure as Code


Terraform handles both small and large infrastructures efficiently. Whether you’re managing a single server or a complex multi-region setup, Terraform’s declarative approach and state management capabilities ensure that your infrastructure can grow and evolve seamlessly.


Infrastructure as code ensures consistent environments across different stages (development, testing, production). By defining your infrastructure in code, you eliminate the risk of configuration drift and ensure that all environments are provisioned identically.


The modular design promotes reusability and simplifies management. Modules can be shared across projects or even organisations, promoting best practices and reducing duplication of effort.

Version Control

Configuration files can be version-controlled using Git, allowing for tracking changes and collaboration. This brings the benefits of version control – such as change history, branching, and code review – to infrastructure management.


In conclusion, Terraform provides a powerful and flexible solution for managing infrastructure as code. At DigitalCloudAdvisor, we utilise Terraform to help our clients achieve efficient, scalable, and compliant infrastructures, whether for a simple web application or a complex multi-tier architecture.

The benefits of using Terraform for infrastructure as code extend beyond just automation. It brings software engineering practices to infrastructure management, enabling teams to treat infrastructure with the same rigour and discipline as application code. This results in more reliable, reproducible, and maintainable infrastructure.

As cloud infrastructures continue to grow in complexity, tools like Terraform become increasingly essential. They enable organisations to manage this complexity, ensure consistency across environments, and rapidly adapt to changing requirements.

Please speak with us today to find out how we can assist you in automating your infrastructure with Terraform. Our team of experts can help you design, implement, and maintain a Terraform-based infrastructure as a code solution tailored to your specific needs, ensuring that you can fully leverage the power of cloud computing while maintaining control, security, and efficiency.

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