Infrastructure as Code with Terraform: From Zero to Production

What is Infrastructure as Code?

Infrastructure as Code (IaC) means managing your servers, networks, and cloud resources through version-controlled configuration files rather than manual clicks in a console. Terraform is the industry standard for this.

Why Terraform?

• Provider-agnostic: works with AWS, Azure, GCP, and 1000+ providers
• Declarative: describe the desired state, Terraform figures out how to get there
• State management: tracks what's currently deployed vs. what's defined

Project Structure

terraform/
├── modules/
│   ├── vpc/
│   │   ├── main.tf
│   │   ├── variables.tf
│   │   └── outputs.tf
│   └── ec2/
│       ├── main.tf
│       ├── variables.tf
│       └── outputs.tf
├── environments/
│   ├── staging/
│   │   ├── main.tf
│   │   └── terraform.tfvars
│   └── production/
│       ├── main.tf
│       └── terraform.tfvars
└── backend.tf

Remote State Configuration

Always use remote state in production:

# backend.tf
terraform {
  backend "s3" {
    bucket         = "my-terraform-state"
    key            = "production/terraform.tfstate"
    region         = "ap-southeast-1"
    encrypt        = true
    dynamodb_table = "terraform-locks"
  }
}

Creating a VPC Module

# modules/vpc/main.tf
resource "aws_vpc" "main" {
  cidr_block           = var.vpc_cidr
  enable_dns_hostnames = true
  enable_dns_support   = true

  tags = {
    Name        = "${var.project_name}-vpc"
    Environment = var.environment
    ManagedBy   = "terraform"
  }
}

resource "aws_subnet" "private" {
  count             = length(var.availability_zones)
  vpc_id            = aws_vpc.main.id
  cidr_block        = cidrsubnet(var.vpc_cidr, 8, count.index)
  availability_zone = var.availability_zones[count.index]

  tags = {
    Name = "${var.project_name}-private-${count.index + 1}"
  }
}

Using the Module

# environments/production/main.tf
module "vpc" {
  source = "../../modules/vpc"

  project_name       = "myapp"
  environment        = "production"
  vpc_cidr           = "10.0.0.0/16"
  availability_zones = ["ap-southeast-1a", "ap-southeast-1b", "ap-southeast-1c"]
}

Key Terraform Commands

# Initialize (download providers and modules)
terraform init

# Preview changes without applying
terraform plan -var-file=terraform.tfvars

# Apply changes
terraform apply -var-file=terraform.tfvars

# Destroy infrastructure
terraform destroy -var-file=terraform.tfvars

# Show current state
terraform show

Best Practices

1. Never commit terraform.tfstate — use remote state (S3 + DynamoDB)
2. Use workspaces or separate directories per environment
3. Pin provider versions to prevent unexpected upgrades
4. Tag every resource with project, environment, and managed-by
5. Use terraform fmt to maintain consistent formatting in CI