Terraform Best Practices

Terraform best practices exist because infrastructure code fails differently from application code. A bad commit in an app usually means a bug you can roll back. A bad Terraform apply can delete a database, replace a load balancer that customers are hitting, or leak a password into a state file that half the company can read. The tool will do exactly what the configuration and the state say, so most of the craft is making sure both are right before anything is applied.

This guide follows the order you meet these problems. It starts with how to lay out and format configuration so reviews are easy, then how to pin Terraform, provider and module versions so a run next month behaves like a run today. The middle chapters cover state, which is the part that hurts most when it goes wrong: remote backends, locking, encryption and splitting state into safe pieces, then secrets and why marking a value sensitive is not the same as keeping it out of state. The last chapters cover modules and refactoring without destroying resources, and a workflow where every change is planned, reviewed, tested and checked against policy.

Every practice was checked against the current Terraform documentation on developer.hashicorp.com, including the official style guide, the pages on sensitive data, the S3 backend, refactoring with moved blocks, import blocks, the dependency lock file, version constraints and the testing framework. Each one tells you what to do, what to avoid and how to check it, with HCL you can adapt.

The advice applies whether you run Terraform from a laptop, from CI or through HCP Terraform. Where a practice depends on a paid feature, it says so and gives the open alternative.