“Engineers don’t intentionally overspend on cloud resources; they simply lack visibility into price tags. Infracost puts the exact monthly cost delta directly inside the Pull Request.”

During cloud architecture advisory at Kyndryl, a developer accidentally modified a Terraform module to deploy premium 64-core Azure Virtual Machines instead of standard burstable instances, resulting in a $12,000 surprise on the monthly invoice.

Architecture: Shift-Left FinOps with Infracost

We embedded Infracost into our automated GitHub Actions workflow to parse Terraform HCL code and calculate precise cost differences.

1. Pre-Apply Cost Parsing: Infracost analyzes terraform plan output files against Azure price APIs.
2. Automated PR Cost Comment: Automatically posts a markdown table to the GitHub PR showing baseline monthly cost, new proposed cost, and total percentage change.

[!TIP] Configure a FinOps threshold rule in GitHub Actions that requires secondary approval from an Architecture Lead if a PR increases monthly spend by over $500.

# # Infracost CLI Command Executed in GitHub Actions Workflow
infracost diff --path=tfplan.json --format=json --out-file=infracost-policy.json
infracost comment github --path=infracost-policy.json --repo=$GITHUB_REPOSITORY --github-token=$GITHUB_TOKEN --pull-request=$PR_NUMBER

The Verdict

Key Takeaway

Embed Infracost PR Delta Comments to Enforce FinOps Discipline at the Code Level.

Integrating Infracost cost estimation provides developers with real-time price feedback, eliminating bill shock before infrastructure is deployed.