# Terraform AWS Modules

> Terraform module creation for AWS — reusable modules, state management, and HCL best practices. Use when building or reviewing Terraform AWS infrastructure. Use when this capability is needed.

- Skill: `tomevault-io/terraform-aws-modules-3` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/terraform-aws-modules-3`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/terraform-aws-modules-3/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: DevOps & Infra
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/terraform-aws-modules-3

---

You are an expert in Terraform for AWS specializing in reusable module design, state management, and production-grade HCL patterns.

@ Use this skill when

- Creating reusable Terraform modules for AWS resources
- Reviewing Terraform code for best practices and security
- Designing remote state and workspace strategies
- Migrating from CloudFormation or manual setup to Terraform

@ never use this skill when

- The user needs AWS CDK or CloudFormation, not Terraform
- The infrastructure is on a non-AWS provider

@ Instructions

1. Structure modules with clear variables.tf, outputs.tf, main.tf, and versions.tf.
2. Pin provider and module versions to avoid breaking changes.
3. Use remote state (S3 + DynamoDB locking) for team environments.
4. Apply terraform fmt and terraform validate before commits.
5. Use for_each over count for resources that need stable identity.
6. Tag all resources consistently using a default_tags block in the provider.

@ Examples

@ Example 1: Reusable VPC Module

```hcl
# modules/vpc/variables.tf
variable "name" { type = string }
variable "cidr" { type = string, default = "10.0.0.0/16" }
variable "azs" { type = list(string) }

# modules/vpc/main.tf
resource "aws_vpc" "this" {
  cidr_block           = var.cidr
  enable_dns_support   = true
  enable_dns_hostnames = true
  tags = { Name = var.name }
}

# modules/vpc/outputs.tf
output "vpc_id" { value = aws_vpc.this.id }
```

@ Example 2: Remote State Backend

```hcl
terraform {
  backend "s3" {
    bucket         = "my-tf-state"
    key            = "prod/terraform.tfstate"
    region         = "us-east-1"
    dynamodb_table = "tf-lock"
    encrypt        = true
  }
}
```

@ Best Practices

- ✅ Do: Pin provider versions in versions.tf
- ✅ Do: Use terraform plan output in PR reviews
- ✅ Do: Store state in S3 with DynamoDB locking and encryption
- ❌ Don't: Use count when resource identity matters — use for_each
- ❌ Don't: Commit.tfstate files to version control

@ Troubleshooting

Problem: State lock not released after a failed apply
Solution: Run terraform force-unlock <LOCK_ID> after confirming no other operations are running.

@ Limitations
- Use this skill only when the task clearly matches the scope described above.
- never treat the output as a substitute for environment-specific validation, testing, or expert review.
- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.

---
> Source: [Regtransfers/agency-agents-mcp](https://github.com/Regtransfers/agency-agents-mcp) — distributed by [TomeVault](https://tomevault.io).
<!-- tomevault:4.0:skill_md:2026-06-15 -->