Senior Software Engineer, Back-end (Fraud)

About the role

Affirm is hiring a Senior Software Engineer for its Fraud Engineering organization, which builds the software that helps Affirm respond to fraud in real time and after the transaction. The role sits in the Fraud International Team, which extends the Fraud Decisioning System to markets outside the US (Canada, the UK, Australia and others). It is fully remote, based in Spain, with collaboration across North American teams in Product, Compliance, Machine Learning, Fraud Operations and Fraud Strategy. An on-call rotation is required.

Key responsibilities

• Own and deliver quarterly goals for the team, guiding engineers through ambiguous problems and supporting delivery.
• Design and implement real-time fraud decisioning services and APIs in Python or Kotlin, extending the Fraud Decisioning System to new markets.
• Build and evolve the platform and tooling that lets Affirm launch fraud decisioning in a new country quickly, turning market-by-market setup into a repeatable, low-friction process.
• Integrate region-specific fraud and risk vendors and help operationalize machine learning and AI signals, using modern AI tooling.
• Support peers and stakeholders across the product lifecycle, articulating technical constraints and weighing risks and trade-offs.
• Keep systems running by creating and monitoring metrics, escalating issues and contributing to on-call efforts.
• Foster quality and ownership through code review and design standards, mentoring teammates and leading by example.

Required profile

• 5+ years of experience building backend systems at scale in Python or Kotlin.
• Fluency with AI-driven engineering: directing and orchestrating AI tools and critically evaluating generated code.
• Strong written and verbal communication in distributed teams, with a proactive, ownership-driven mindset.
• Visa sponsorship available, but the candidate must be based in Spain.

Required skills

• Distributed systems and infrastructure with AWS, MySQL/PostgreSQL and Kubernetes.
• SQL and familiarity with CI/CD and safe production deployments.
• Nice to have: Snowflake, dbt, Airflow or Chronosphere; fraud prevention, risk systems or real-time decisioning background; experience building for multiple markets; fintech or regulated-environment experience.

What we offer

• Base pay range of EUR 86,000 to EUR 122,000 per year, plus equity grade 4.
• Monthly stipends for health, wellness and tech spending, and 100% subsidized medical, dental and vision coverage for employees and dependents.
• Flexible spending wallets, away days, learning and development programs, parental benefits and employee resource groups.