Terraform Best Practices for Infrastructure as Code

January 10, 2025•

3 min read

#terraform#iac#devops#aws#cloud

After years of managing infrastructure across AWS, Azure, and GCP with Terraform, I've compiled the most impactful best practices that have saved countless hours and prevented numerous production issues.

1. State Management

Never store Terraform state locally in production. Always use remote backends with state locking.

hcl

terraform {
  backend "s3" {
    bucket         = "terraform-state-prod"
    key            = "infrastructure/terraform.tfstate"
    region         = "us-east-1"
    encrypt        = true
    dynamodb_table = "terraform-locks"
  }
}

2. Module Structure

Organize your code into reusable modules for consistency and maintainability.

code

.
├── modules/
│   ├── vpc/
│   │   ├── main.tf
│   │   ├── variables.tf
│   │   └── outputs.tf
│   └── eks/
│       ├── main.tf
│       ├── variables.tf
│       └── outputs.tf
└── environments/
    ├── dev/
    ├── staging/
    └── prod/

3. Variable Validation

Use variable validation to catch configuration errors early.

hcl

variable "environment" {
  type        = string
  description = "Environment name"

  validation {
    condition     = contains(["dev", "staging", "prod"], var.environment)
    error_message = "Environment must be dev, staging, or prod."
  }
}

4. Output Sensitive Data Carefully

Mark sensitive outputs appropriately to prevent accidental exposure.

hcl

output "database_password" {
  value       = aws_db_instance.main.password
  sensitive   = true
  description = "Database master password"
}

5. Use Data Sources

Leverage data sources to reference existing infrastructure instead of hardcoding values.

hcl

data "aws_ami" "amazon_linux" {
  most_recent = true
  owners      = ["amazon"]

  filter {
    name   = "name"
    values = ["amzn2-ami-hvm-*-x86_64-gp2"]
  }
}

6. Implement Proper Tagging

Consistent tagging enables cost tracking, resource management, and automation.

hcl

locals {
  common_tags = {
    Environment = var.environment
    ManagedBy   = "Terraform"
    Project     = var.project_name
    CostCenter  = var.cost_center
  }
}

resource "aws_instance" "app" {
  # ... other configuration ...
  tags = merge(local.common_tags, {
    Name = "app-server-${var.environment}"
  })
}

7. Use Workspaces for Environments

Terraform workspaces can simplify multi-environment management.

bash

terraform workspace new staging
terraform workspace select production
terraform plan -var-file="prod.tfvars"

8. Automate with CI/CD

Integrate Terraform into your CI/CD pipeline for consistent deployments.

yaml

# .gitlab-ci.yml
terraform_plan:
  stage: plan
  script:
    - terraform init
    - terraform plan -out=tfplan
  artifacts:
    paths:
      - tfplan

terraform_apply:
  stage: apply
  script:
    - terraform apply tfplan
  when: manual
  only:
    - main

Conclusion

These practices have proven invaluable in maintaining large-scale infrastructure. Start with state management and module structure—they provide the foundation for everything else.

Remember: Infrastructure as Code is code. Apply the same software engineering principles you'd use for application development.