5 Terraform Best Practices Every DevOps Engineer Should Know

Infrastructure as Code (IaC) has revolutionized how we manage cloud resources, and Terraform has emerged as the go-to tool for many organizations. However, writing Terraform code that's maintainable, secure, and scalable requires following certain best practices.

In this post, we'll cover five essential Terraform best practices that every DevOps engineer should implement.

1. Use Remote State with Locking

One of the most critical mistakes teams make is storing Terraform state locally. This leads to conflicts, lost state, and potential security risks.

Always use remote state with a backend that supports locking:

Terraform

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

💡

Enable encryption for your state files—they often contain sensitive information like passwords and API keys.

2. Structure Your Code with Modules

Don't repeat yourself. If you're copying and pasting Terraform code, it's time to create a module.

A well-structured module looks like this:

Plain Text

modules/
└── vpc/
    ├── main.tf
    ├── variables.tf
    ├── outputs.tf
    └── README.md

Then use it across environments:

Terraform

module "prod_vpc" {
  source = "./modules/vpc"
  
  environment = "production"
  cidr_block  = "10.0.0.0/16"
}

module "staging_vpc" {
  source = "./modules/vpc"
  
  environment = "staging"
  cidr_block  = "10.1.0.0/16"
}

3. Implement Proper Variable Validation

Don't just define variables—validate them. This catches errors early before they cause infrastructure issues.

Terraform

variable "environment" {
  type        = string
  description = "The deployment environment"
  
  validation {
    condition     = contains(["dev", "staging", "prod"], var.environment)
    error_message = "Environment must be dev, staging, or prod."
  }
}

variable "instance_count" {
  type        = number
  description = "Number of instances to create"
  
  validation {
    condition     = var.instance_count > 0 && var.instance_count <= 10
    error_message = "Instance count must be between 1 and 10."
  }
}

4. Use Workspaces or Directory Structure for Environments

There are two main approaches to managing multiple environments:

Option A: Workspaces

Bash

terraform workspace new staging
terraform workspace new production
terraform workspace select production

Option B: Directory Structure (Recommended)

Plain Text

infrastructure/
├── modules/
├── environments/
│   ├── dev/
│   │   ├── main.tf
│   │   └── terraform.tfvars
│   ├── staging/
│   │   ├── main.tf
│   │   └── terraform.tfvars
│   └── prod/
│       ├── main.tf
│       └── terraform.tfvars

⚠️

Workspaces share the same backend configuration, which can be risky for production environments. The directory approach provides better isolation.

5. Implement a Consistent Tagging Strategy

Tags are essential for cost allocation, security compliance, and resource management. Create a local variable for common tags:

Terraform

locals {
  common_tags = {
    Project     = var.project_name
    Environment = var.environment
    ManagedBy   = "terraform"
    Owner       = var.team_name
    CostCenter  = var.cost_center
  }
}

resource "aws_instance" "web" {
  ami           = var.ami_id
  instance_type = var.instance_type
  
  tags = merge(local.common_tags, {
    Name = "${var.project_name}-web-${var.environment}"
    Role = "webserver"
  })
}

Bonus: Use Pre-commit Hooks

Automate code quality checks with pre-commit hooks:

YAML

# .pre-commit-config.yaml
repos:
  - repo: https://github.com/antonbabenko/pre-commit-terraform
    rev: v1.83.5
    hooks:
      - id: terraform_fmt
      - id: terraform_validate
      - id: terraform_tflint
      - id: terraform_docs

Conclusion

Following these best practices will help you write Terraform code that's:

Maintainable — Easy to update and extend
Secure — Protected state and validated inputs
Scalable — Ready for multiple environments
Collaborative — Works well in team settings

At A2DevOps, we help teams implement these practices and more. If you're struggling with your infrastructure code or want to level up your IaC game, book a consultation with us.

What Terraform challenges are you facing? We'd love to hear about them.