Affirm
Senior
Affirm Senior Backend Engineer interview: leading engineers on a checkout-critical Merchant Data Platform serving millions of requests a day
This interview targets Affirm's Senior Software Engineer role on the fully remote European Merchant Data Platform team, which owns merchant identity and onboarding data across a checkout-critical, high-availability service. Expect questions on distributed systems design (Python/Kotlin, AWS, MySQL, Kubernetes), leading engineers through ambiguous open-ended problems, and owning availability/reliability SLAs. Strong answers show hands-on architecture decisions at scale plus real mentoring and cross-functional delivery leadership, not just individual coding ability.
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What this interview tests
- Highly available, low-latency distributed backend systems (Python/Kotlin, AWS, MySQL, Kubernetes)
- Leading engineers through ambiguous, open-ended technical problems
- Making safe, significant changes in a large existing codebase
- Owning system availability, reliability, and on-call response
- Schema/API evolution for merchant identity data without breaking downstream consumers (fraud/risk pipelines)
- Mentoring engineers via code and design review
Common question themes
Walk me through a highly available distributed system you designed and its SLA
Describe leading a team through an ambiguous problem to hit a quarterly goal
Tell me about a risky change you made safely in a large codebase — what practices did you use
How would you evolve a merchant identity schema without breaking downstream fraud/risk consumers
Walk me through a production incident you owned, from triage to postmortem
Describe mentoring an engineer through a design or code review disagreement