Interview Infrastructure as Code (Terraform, Ansible)

What is a policy-as-code check for Terraform (OPA, Sentinel, checkov)?

Infrastructure as Code (Terraform, Ansible) · Intermediate level

Answer

Policy-as-code checks evaluate Terraform plans or configuration against organizational rules. Examples include OPA/Rego, Sentinel, Checkov, Conftest, and tfsec-style checks. They catch issues such as public S3 buckets, unencrypted storage, unrestricted security groups, missing tags, and disallowed instance types before apply.

Technical explanation

Evaluate both configuration and generated plan JSON where possible; plan checks catch computed behavior.

Policies should be clear, versioned, tested, and owned like application code.

Start with high-value controls: encryption, public access, IAM wildcards, tagging, and destructive changes.

Keep Terraform's ownership boundary clear: one state should own a resource or field, and other tools should consume published outputs instead of modifying it.

Use fmt, validate, linting, policy checks, plan review, and state locking before production applies.

Design for small blast radius by splitting state around lifecycle, permissions, and recovery boundaries.

Hands-on example

1. Build a safe IaC delivery workflow for: What is a policy-as-code check for Terraform (OPA, Sentinel, checkov)?

2. Pull request job:

terraform fmt -check

terraform init -backend=false

terraform validate

tflint --recursive

checkov -d .

terraform init

terraform plan -out=tfplan

terraform show -json tfplan > tfplan.json

3. Policy job evaluates plan JSON for public exposure, missing encryption, IAM wildcards, and destructive changes.

4. Apply job runs only after approval, uses remote state locking, short-lived cloud credentials, and applies the saved plan artifact.

5. For failures, rerun plan, inspect state and cloud objects, and fix root cause before any state surgery.

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