Using Terraform to provision infrastructure is increasingly common. The next level of maturity, treating Terraform configuration as the authoritative system of record for infrastructure, requires practices that go beyond writing .tf files.
State management is everything
Terraform's state file is the source of truth for what infrastructure exists. Corrupted or lost state means Terraform cannot manage the resources it created. Remote state with locking (S3 + DynamoDB on AWS, Azure Blob Storage + lease, Terraform Cloud) prevents simultaneous modifications and provides a durable state store. The teams that manage Terraform state correctly have no infrastructure incidents from state corruption; the teams that do not eventually do.
Modules as reusable infrastructure components
Terraform modules are reusable, composable infrastructure components. A module for a standard VPC configuration, parameterised with CIDR range and availability zones, can be used across all your cloud environments without duplication. Module versioning in a private Terraform registry or via git tags enables controlled updates: teams consume a specific module version, and upgrades go through a review process.
Drift detection and remediation
Configuration drift occurs when infrastructure is modified outside of Terraform. Someone changes a security group rule in the console, or a cloud event autoscales a resource group. Terraform plan shows the drift. The question is remediation: do you update the Terraform configuration to match the manual change, or do you revert the manual change to match the configuration? The answer depends on whether the manual change was intentional and correct. Drift detection in CI/CD pipelines (running terraform plan on a schedule and alerting on unexpected diffs) is the observability for infrastructure state.
Testing Terraform configurations
Testing Terraform before applying it reduces infrastructure incidents. Three levels of testing: linting (tflint for syntax and best practice violations), validation (terraform validate for configuration correctness), and integration testing (Terratest or terraform test for actually provisioning and verifying infrastructure in a test environment). The investment in testing increases with the blast radius of the configuration: a module that is used across 50 environments is worth thorough testing.