Terraform Modular Project Structure

Reusable modules, remote state, team-ready. Designed for large infrastructure and multiple projects.

#terraform #iac #devops #modular #enterprise

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Project Directory

terraform/

modules/

Reusable infrastructure modules

networking/

vpc/

main.tf

variables.tf

outputs.tf

versions.tf

README.md

security-groups/

main.tf

variables.tf

outputs.tf

compute/

ec2/

main.tf

variables.tf

outputs.tf

ecs/

main.tf

variables.tf

outputs.tf

data/

rds/

main.tf

variables.tf

outputs.tf

s3/

main.tf

variables.tf

outputs.tf

live/

Actual deployments

dev/

us-east-1/

Region-specific

networking/

terragrunt.hcl

services/

api/

terragrunt.hcl

env.hcl

Environment vars

prod/

us-east-1/

networking/

services/

eu-west-1/

Multi-region

networking/

services/

env.hcl

terragrunt.hcl

Root config

global/

Account-wide resources

iam/

dns/

s3-state/

State bucket bootstrap

Why This Structure?

Enterprise-grade structure using Terragrunt for DRY configurations. modules/ contains versioned, tested modules. live/ deploys those modules per environment and region. This scales to hundreds of resources across multiple accounts.

Key Directories

modules/-Reusable modules, versioned separately
live/-Actual deployments organized by env/region
live/*/env.hcl-Environment-specific variables
global/-Account-wide resources like IAM, DNS
terragrunt.hcl-DRY configuration with Terragrunt

Terragrunt Config

# live/prod/us-east-1/services/api/terragrunt.hcl
include "root" {
  path = find_in_parent_folders()
}

terraform {
  source = "../../../../../modules/compute/ecs"
}

inputs = {
  cluster_name   = "api-prod"
  instance_count = 3
  instance_type  = "t3.large"
}

Getting Started

Install Terraform and Terragrunt
Bootstrap state bucket in global/s3-state/
Create first module in modules/
Deploy via live/dev/ with Terragrunt
cd live/dev/us-east-1/networking && terragrunt apply

When To Use This

Large infrastructure (100+ resources)
Multiple AWS accounts and regions
Infrastructure team with many members
Need module versioning and testing
Compliance requires audit trails

Trade-offs

Complexity-Steeper learning curve, more tooling
Terragrunt dependency-Additional tool to maintain
Initial setup-More upfront work before first deploy

Testing Strategy

Module tests-Use Terratest or tftest for module validation
Plan review-Always plan before apply in CI
Policy as code-OPA or Sentinel for compliance checks
Drift detection-Scheduled plans to detect manual changes