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. Everything here applies to OpenTofu as well: it's a drop-in fork of Terraform, so just run tofu instead of terraform.

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 {
  required_version = ">= 1.10"

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

use_lockfile = true enables S3-native state locking, so you no longer need a separate DynamoDB table. It requires Terraform 1.10 or later, and 1.11+ is the recommended baseline since that release deprecated the dynamodb_table argument. OpenTofu supports use_lockfile too (OpenTofu 1.10+). Older setups that used DynamoDB for locking can migrate by adding use_lockfile = true and then removing dynamodb_table.

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:

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

Then use it across environments:

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.

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#

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

Option B: Directory Structure (Recommended)#

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

5. Implement a Consistent Tagging Strategy#

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

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:

# .pre-commit-config.yaml
repos:
  - repo: https://github.com/antonbabenko/pre-commit-terraform
    rev: v1.109.4  # pin to the latest release
    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.