Senior Software Engineer, Backend (Test Enablers)

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 platform so it is reliable, observable, and easier for other teams to adopt.
• Partner with product engineering and infrastructure teams to improve test signal quality, reduce false failures, and support faster validation loops.
• Lead medium-to-large technical projects from ambiguous problem definition through design, implementation, rollout, and operational ownership.
• Improve reliability and operational maturity through dashboards, SLOs, alerts, runbooks, and clear ownership models.
• Reduce manual operational load for load testing, including test data creation, environment setup, reporting, and failure diagnosis.
• Write high-quality, maintainable code that can be easily understood and extended by others.
• Contribute to technical specs, RFCs, ADRs, project plans, and other async artifacts that align teams around technical decisions.
• Review code and technical designs, provide constructive feedback, and help raise engineering standards.
• Mentor engineers and help build a culture of practical testing excellence.

What We Look For

• 5+ years of software engineering experience.
• Strong backend engineering experience with Python, Kotlin, Java, or similar languages.
• Experience designing, building, and operating distributed systems, platform infrastructure, internal developer tools, or testing infrastructure.
• Strong ownership and ability to independently drive ambiguous technical work to completion.
• Experience improving system reliability, observability, operational maturity, and maintainability.
• Ability to collaborate across engineering teams and influence technical direction through clear communication.
• Excellent written and verbal communication skills, including async artifacts such as technical specs, RFCs, ADRs, and project plans.
• Strong engineering fundamentals across system design, testing, debugging, reliability, and production operations.
• Operational ownership of critical internal testing platforms, including reliability, observability, alerting, runbooks, and incident readiness.
• Experience with test automation frameworks, test data systems, mocks, contract testing, integration testing, load testing and CI/CD platforms.
• Ability to balance pragmatic delivery with long-term technical quality.
• Passion for improving developer productivity and product quality through scalable, automated, reliable systems.

Compensation & Benefits

Base Pay Grade - N

Equity Grade - 4

Employees new to Affirm typically come in at the start of the pay range. Affirm focuses on providing a simple and transparent pay structure which is based on a variety of factors, including location, experience and job-related skills. 

Base pay is part of a total compensation package that may include monthly stipends for health, wellness and tech spending, and benefits (including 100% subsidized medical coverage, dental and vision for you and your dependents). In addition, the employees may be eligible for equity rewards offered by Affirm Holdings, Inc. (parent company).

ESP base pay range per year: €86,000  -  €122,000    

Additional benefits include:

• Flexible Spending Wallets for tech, food and lifestyle
• Away Days - wellness days to take off work and recharge
• Learning & Development programs
• Parental benefits
• Employee Resource & Community Groups

We are able to offer visa sponsorship for this role, but do require that someone is based in Spain for the role.