Build the money-movement systems behind Affirm's debit card and BNPL flows

Affirm's Money Movement & Card Ledger team builds the systems that move money, integrate bank data, and manage merchant data behind Affirm Card and its buy-now-pay-later financing. The interview looks for someone with about 2.5+ years of backend experience in Python or Kotlin who can design correct, scalable APIs, take ownership of a piece of a larger project, and hold up their end during on-call.

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What this interview tests

API design for financial/ledger systems (correctness, idempotency)
Python or Kotlin backend proficiency
Distributed systems building blocks (AWS, MySQL, Kubernetes)
Breaking down and phasing larger projects
On-call and operational ownership
Cross-functional communication with product/design/analytics

Common question themes

Design an API for tracking money movement between a bank and a merchant

How do you ensure idempotency when a payment or ledger entry might be retried

Tell me about a time you had to debug someone else's code

Describe breaking a large project into deliverable phases

How would you monitor a critical money-movement service for issues

How candidates describe it

Real Software Engineer II (Money Movement & Card Ledger) interview stories — retold from candidates' public write-ups, with sources.

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