Senior Software Engineer, Back-end (Fraud)

Affirm is reinventing credit to make it more honest and friendly, giving consumers the flexibility to buy now and pay later without any hidden fees or compounding interest.

The Fraud Engineering organization builds the foundational and tactical software that enables Affirm to respond strategically to fraud—both in real time and after the transaction. Their mission is to support business growth while protecting Affirm, buyers, and merchants by evaluating risk at critical decision points, adapting to evolving fraud patterns, and equipping operations teams with tools to investigate and mitigate fraud at scale.

The team is fully remote based in Europe and collaborates closely with stakeholders across North America including Product, Compliance, Machine Learning, Fraud Operations, Fraud Strategy, and other Fraud Engineering teams.

• 5+ years of experience building backend systems at scale using Python or Kotlin.
• Experience with distributed systems and infrastructure using AWS, MySQL/PostgreSQL, and Kubernetes.
• Strong system design skills and a track record of delivering maintainable, extensible services.
• Proficiency in SQL and working with data-rich environments.
• Familiarity with CI/CD practices and safe production deployments.
• Strong written and verbal communication skills, especially in distributed teams.
• A proactive, ownership-driven mindset with a focus on learning and team success.

Nice to have:

• Experience with Snowflake, dbt, Airflow, or Chronosphere.
• Background in fraud prevention, risk systems, or post-transaction tooling.
• Experience working in the fintech sector or other highly regulated environments, with a strong understanding of risk, compliance, and operational constraints.

• Own and deliver quarterly goals for the team.
• Lead engineers through ambiguity to solve open-ended problems.
• Ensure support for team members throughout delivery.
• Design and implement backend services and APIs using Python or Kotlin within Affirm’s microservice and event-driven architecture.
• Shape the team’s roadmap, collaborate on technical design, and drive execution across projects spanning multiple teams.
• Partner with the Engineering Manager and teammates to elevate quality standards, evolve engineering processes, and represent the team in cross-functional initiatives.
• Collaborate cross-functionally with stakeholders in Fraud Ops, Compliance, Product, Machine Learning, and Analytics to build scalable fraud tooling and infrastructure.
• Proactively identify opportunities to improve system reliability, team efficiency, or architecture and lead efforts to address them.
• Contribute to operational excellence by maintaining high observability standards, responding to incidents, and participating in the on-call rotation.
• Foster a culture of ownership, inclusion, and craftsmanship by mentoring teammates, providing feedback, and upholding high code and design standards.
• Participate in on-call rotation as a requirement.

• This role is located in Poland and is remote within the country.
• Affirm is a remote-first company with most roles remote but some requiring occasional office presence.
• Affirm provides reasonable accommodations during the hiring process for candidates with disabilities.
• Affirm considers qualified applicants with arrest and conviction records pursuant to specific city ordinances for U.S. positions.