Review both the infrastructure-as-code diff and the plan it produces. Confirm that each planned addition, update, replacement, or deletion matches the stated intent; assess security, state handling, operational impact, and automated checks. Treat the plan in a pull request as provisional: after merge, inspect the concrete plan again before applying it.
1. Establish what the change is meant to do
Before examining resource details, identify the affected environment, the problem being solved, and the expected outcome. Read the change description alongside the relevant dependencies and ownership information. A useful review can answer: what should change, where should it change, and how will the team know the result is correct?
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- Check that the scope and target environment are clear.
- Look for dependencies on other modules, services, or changes in the same workflow.
- Ask for clarification when the intended outcome or operational owner is not apparent.
2. Read the configuration diff
Review the code itself, not just the summary of its planned effects. Examine resource declarations and changes to modules, providers, input defaults, permissions, network exposure, storage, encryption, secrets, and dependencies. Check that the change is scoped and consistent with team conventions.
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- Verify that permissions are limited to the actions and resources the workload requires.
- Check whether a change exposes a service or data more broadly than intended.
- Look at how credentials and sensitive values enter the configuration, and whether outputs or state could reveal them.
- Review storage and encryption settings in the context of the data and environment affected.
Scope and dependencies
Check whether defaults, provider changes, or shared-module edits could affect resources beyond the ones named in the pull request. Confirm that dependencies and resource relationships still express the intended ordering and lifecycle.
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3. Compare the plan with the intent
A Terraform plan is evidence of expected infrastructure effects, not simply a recap of edited lines. Compare every proposed action with the change description. HashiCorp’s core workflow guidance explains the write-plan-apply process and cautions that a plan reviewed in a pull request can differ from the final plan because of merge order or intervening infrastructure changes.
Inspect each kind of action
- Additions: Are the new resources expected, correctly scoped, and connected to the right dependencies?
- Updates: Do the changed attributes produce the desired result without altering unrelated behavior?
- Replacements: Does the replacement make sense, and could it cause downtime, data loss, or a temporary capacity gap?
- Deletions: Is each removal intentional, and have dependent services, data, and recovery needs been considered?
Also notice resource counts, unknown values, and dependency changes. If the plan does not make the consequences clear enough to assess, ask for additional explanation rather than treating uncertainty as approval.
Consider timing and operational impact
Assess whether the change could interrupt service, affect a critical dependency, or expose or alter data. For a consequential apply, consider whether it needs a maintenance window, advance notification, monitoring, or coordination with another owner. HashiCorp’s workflow guidance discusses risk, timing, and monitoring as part of planning infrastructure changes.
4. Assess security checks and policy evidence
Review the results of applicable source scans, infrastructure scans, and policy checks. AWS recommends scanning infrastructure and source code and using policy checks as governance guardrails in its Terraform security best practices.
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A passing check is useful evidence, but it does not decide whether the proposed change is safe for this workload. Confirm that findings are understood, relevant issues are resolved or explicitly accepted through the team’s process, and the checks actually cover the configuration and plan under review.
What policy checks can and cannot establish
AWS describes using Open Policy Agent (OPA) to evaluate structured Terraform plan JSON against policy logic. Such checks can catch some prohibited or nonconforming changes before deployment, but they do not replace runtime monitoring, organizational guardrails, or controls on deployed resources. See AWS’s guidance on pattern-based policy as code.
Policy frameworks and platform support can change. HashiCorp’s policy overview lists Terraform policy, Sentinel, and OPA, and labels Terraform policy beta on that page. Check current status and support before relying on a specific framework for production enforcement.
5. Check state and execution controls
Terraform state can contain sensitive values, so review who and what can access it and how the selected backend protects it. Confirm that the backend’s capabilities and configuration suit the team’s security requirements, and that locking is supported and enabled where concurrent operations could conflict. HashiCorp covers remote state, encryption, and locking in its Terraform collaboration guidance.
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Make sure the execution path is clear: who or what can apply the change, which approvals are required, and whether the reviewed plan is the one that will be used. A plan review is not a substitute for controlled access to deployment.
6. Approve the change against evidence
Base approval on the intent, diff, plan, security evidence, and execution controls together. Record unresolved risks or required follow-up in the review rather than relying on an unspoken assumption. AWS Well-Architected recommends defining review timing, participants, criteria, approval rules, and ways to improve the process in its guidance on conducting code reviews.
After merge, review the concrete plan against the latest configuration and shared state before applying. If it differs materially from the plan that was reviewed, assess the difference and obtain any required renewed approval. For higher-risk changes, coordinate monitoring and notifications around the apply.
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Reviewer checklist
- Does the change description state the intent, scope, target environment, and expected outcome?
- Does the plan match that intent, without unexplained replacements or destruction?
- Could the change disrupt service, expose data, widen network access, or alter a critical dependency?
- Are permissions scoped to the workload’s required actions and resources?
- Are secrets kept out of source and state where possible, and are sensitive outputs handled appropriately?
- Have applicable scans and policy checks run, and are their findings understood and addressed?
- Are state protection, access controls, and locking appropriate for the selected backend?
- Are reviewers, approvals, and the apply path clear—and will the post-merge plan be checked before execution?
Adapt the checklist to the providers, criticality, and control requirements of the environment. A useful team process makes review criteria and approval responsibilities explicit, then revisits them as the workflow changes.
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