Senior Software Engineer, Back-end (Fraud)

About the Role

Affirm is reinventing credit to make it more honest and friendly, enabling consumers to buy now and pay later without hidden fees or compounding interest. The Fraud Engineering organization builds foundational and tactical software that enables Affirm to respond strategically to fraud in real time and after transactions, supporting business growth while protecting Affirm, buyers, and merchants.

We're seeking a Senior Software Engineer to join our fully remote team based in Poland. You'll collaborate closely with stakeholders across North America, including teams in Product, Compliance, Machine Learning, Fraud Operations, Fraud Strategy, and other Fraud Engineering teams.

About the Fraud International Team

The Fraud International Team (FIT) leads the engineering effort to extend Affirm's Fraud Decisioning System into markets beyond the US—Canada, the UK, Australia, and beyond. The team owns real-time fraud decisioning for these markets, integrates region-specific risk vendors, and is building the platform that enables Affirm to stand up fraud protection in new countries quickly and safely.

Responsibilities

• Own and deliver quarterly goals for your team, leading engineers through ambiguity to solve open-ended problems and ensuring support throughout delivery
• Design and implement real-time fraud decisioning services and APIs in Python or Kotlin, extending Affirm's Fraud Decisioning System to markets beyond the US
• Build and evolve the platform and tooling that enables Affirm to launch fraud decisioning in a new country quickly—transforming market-by-market setup (rules, models, and vendor configuration) into a repeatable, low-friction path so launches scale efficiently
• Integrate region-specific risk vendors and adapt the decisioning system to local regulatory and market requirements
• Equip operations teams with tools to investigate and mitigate fraud at scale
• Evaluate risk at critical decision points in the user journey and rapidly adapt to evolving fraud patterns

Requirements

• Senior-level software engineering experience with demonstrated leadership
• Proficiency in Python or Kotlin
• Experience designing and implementing real-time systems and APIs
• Background in fraud prevention, risk management, or financial security (preferred)
• Ability to collaborate effectively across distributed teams and multiple time zones