Shift-Left FinOps: Adding SageMaker Support to Infracost

GitHub PR: infracost/infracost#3567 (open, awaiting upstream review)

“Shift-Left FinOps” is about moving cost visibility as far forward in the development lifecycle as possible. This project involved contributing to Infracost, a tool that sits in the CI/CD pipeline to show engineers the “price tag” of their Terraform changes before they hit production.

The Technical Challenge

AWS SageMaker pricing is complex because it involves multiple billing dimensions that are often opaque in Terraform code. My contribution adds pricing support for aws_sagemaker_endpoint_configuration, covering:

• Inference Variants: Support for both provisioned instance-based hosting and serverless configurations.
• Shadow Production Variants: Mapping costs for test models running in parallel with production traffic—a common source of “bill shock.”
• Async & Data Capture: Accounting for the overhead of asynchronous inference configurations and data capture fees for model monitoring.

Implementation Details

Working in the Go codebase of Infracost, I had to map complex Terraform resource attributes to the AWS Price List API. This required:

1. Resource Mapping: Translating nested configuration blocks into cost components.
2. Logic for Serverless vs. Provisioned: Handling the conditional logic where pricing changes from “per hour” to “per GB/second” based on the serverless_config block.
3. Unit Testing: Ensuring that the pricing engine accurately calculates the monthly estimate across various edge cases (e.g., provisioned concurrency).

Key Learnings

Contributing to a FinOps tool is a masterclass in the “financial underbelly” of the cloud. It forces you to realize that as a software engineer, you are effectively a “financial architect.” Every line of infrastructure code is a spending decision. By building visibility into the PR level, we empower engineers to be proactive rather than reactive.