Terraform Module Design Patterns

Reusable modules, versioning, and interface design for platform teams.

Terraform Module Design Patterns

Module types

Type	Purpose	Example
Resource module	Single logical resource	`terraform-aws-s3-bucket`
Composition module	Product-ready stack	`vpc-app-tier`
Root module	Environment instance	`prod/us-east-1/app`

Interface guidelines

Expose minimal required variables; sensible defaults for optional
Output IDs and ARNs consumers need not entire resource objects
Document breaking changes in CHANGELOG; use semver tags

Example structure


modules/
  networking/vpc/
  compute/eks/
environments/
  prod/
  staging/

CI checks


terraform fmt -check -recursive
terraform validate
tflint
checkov -d .

Anti-patterns

terraform apply from laptops to production
Unpinned module sources (ref=main)
Monolithic state for entire organization