Senior Software Engineer, Back-end (Fraud)

About the Role

Affirm is reinventing consumer credit through transparent buy-now-pay-later financing. The Fraud Engineering organization builds the software that protects Affirm, buyers, and merchants from fraud in real time and post-transaction. We're hiring a Senior Software Engineer to join our fully remote Fraud International Team (FIT), which extends Affirm's fraud decisioning capabilities to markets beyond the US including Canada, the UK, and Australia. You'll collaborate with cross-functional teams across North America including Product, Compliance, Machine Learning, Fraud Operations, and Fraud Strategy.

About the Fraud International Team

FIT owns real-time fraud decisioning for international markets, integrates region-specific risk vendors, and builds the platform infrastructure that enables Affirm to launch fraud protection in new countries rapidly and safely. As Affirm expands globally, the team scales in parallel.

Responsibilities

• Own and deliver quarterly goals for your team, guiding engineers through complex, open-ended problems while ensuring sustained support throughout execution
• Design and implement real-time fraud decisioning services and APIs in Python or Kotlin, extending Affirm's Fraud Decisioning System to new geographic markets
• Build and evolve platform tooling that enables Affirm to launch fraud decisioning in new countries with low friction—converting market-specific setup (rules, models, vendor configuration) into repeatable, scalable processes
• Integrate region-specific fraud risk vendors and third-party services with Affirm's core systems
• Evaluate risk at critical decision points in the user journey and rapidly adapt to evolving fraud patterns
• Equip fraud operations teams with tools for investigation and mitigation at scale

Requirements

• Senior-level software engineering experience with backend systems
• Proficiency in Python or Kotlin
• Experience designing and implementing real-time, high-volume transaction systems
• Track record of leading engineering teams and delivering results in complex, ambiguous environments
• Familiarity with fraud detection, risk decisioning, or financial services systems is a plus

Location & Work Arrangement

Remote based in Spain (fully remote team)