Senior Software Engineer, Backend (Test Enablers)

Affirm is reinventing credit to make it more honest and friendly, giving consumers the flexibility to buy now and pay later without any hidden fees or compounding interest.

We are looking for a highly motivated Senior Software Engineer to join our Test Enablers team within Test Platform Engineering (Developer Productivity).

The Test Enablers team builds and operates the platforms that allow Affirm engineering teams to test with confidence. Our systems provide synthetic identities, test data seeding, mocking, deterministic testing workflows and load testing.

Developer Productivity’s mission is to dramatically accelerate software development at Affirm while keeping our systems reliable for customers. Our long-term north star is to scale to 1,000 PRs per day by December 2027. To reach that goal, Affirm needs validation systems that are fast, trustworthy, automated, and scalable.

This role is central to that effort.

You will design and build platform capabilities that help engineers validate product changes earlier, run safer load tests, reduce reliance on expensive E2E-only validation, and improve the reliability of CI signals. You will also help prepare Affirm’s testing infrastructure for AI-assisted development workflows, where agents and humans need deterministic, observable, and actionable validation feedback.

Affirm is growing fast, and we want you to help us scale our products and engineering systems 10x and beyond through world-class developer productivity infrastructure.

What You’ll Do

Design, build, and maintain scalable systems for synthetic identities, test data seeding, mocking, load testing, and deterministic validation workflows.

Help evolve Affirm’s testing strategy from broad E2E-heavy validation toward a more scalable model with stronger component, integration, contract, performance, and targeted E2E testing.

Build platform capabilities that make production-like load testing safer, more repeatable, and easier to operate.

Improve our test pla