Senior Software Engineer, Back-end (Fraud) Remote Poland

About the Role

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. Our mission is to support business growth while protecting Affirm, our buyers, and our merchants. We evaluate risk at critical decision points in the user journey, rapidly adapt to evolving fraud patterns, and equip operations teams with the tools needed to investigate and mitigate fraud at scale. We’re looking for a Senior Software Engineer to join our fully remote team based in Europe. 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.

Responsibilities

• You will be responsible for owning and delivering quarterly goals for your team, leading engineers through ambiguity to solve open-ended problems, and ensuring that everyone is supported throughout delivery.
• You will design and implement backend services and APIs using Python or Kotlin, operating within Affirm’s microservice and event-driven architecture.
• You will take an active role in shaping the team’s roadmap, collaborating on technical design, and driving execution across projects that span multiple teams.
• You will partner with the Engineering Manager and your teammates to elevate quality standards, evolve engineering processes, and represent the team in cross-functional initiatives.
• You will collaborate cross-functionally with stakeholders in Fraud Ops, Compliance, Product, Machine Learning, and Analytics to build scalable fraud tooling and infrastructure.
• You will proactively identify opportunities to improve system reliability, team efficiency, or architecture—and lead efforts to address them.
• You will contribute to operational excellence by maintaining high observability standards, responding to incidents, and participating in the on-call rotation.
• You will foster a culture of ownership, inclusion, and craftsmanship by mentoring teammates, providing feedback, and upholding high code and design standards.

Requirements

• 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...