Own and deliver quarterly goals for your team, leading engineers through ambiguity to solve open-ended problems, and ensuring that everyone is supported 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 let Affirm launch fraud decisioning in a new country quickly—turning market-by-market setup (rules, models, and vendor configuration) into a repeatable, low-friction path so launches scale sub-linearly with the number of markets.
Integrate region-specific fraud and risk vendors and help operationalize the machine learning and AI signals that power real-time decisioning, while using modern AI tooling to move faster as an engineer.
Support peers and stakeholders across the product development lifecycle - collaborating with Product, Machine Learning, Analytics, and Fraud Strategy, articulating technical constraints, and partnering on decisions that properly weigh risks and trade-offs.
Support the operations and availability of your team's systems by creating and monitoring metrics, escalating when needed, and contributing to keep-the-lights-on and on-call efforts.
Foster a culture of quality and ownership - setting and improving code review and design standards, mentoring teammates, and leading by example.
Participate in on-call rotation as a requirement.

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.
Fluency with AI-driven engineering - every Affirm engineer builds with tools like Claude Code and most PRs are co-authored with AI, so directing and orchestrating AI and excelling in the reviewer's seat (setting intent, critically evaluating generated code, and owning its correctness, quality, and security) is a core expectation.
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.
Experience working in the fintech sector or other highly regulated environments, with a strong understanding of risk, compliance, and operational constraints.

Experience with Snowflake, dbt, Airflow, or Chronosphere.
Background in fraud prevention, risk systems, or real-time decisioning.
Experience building for multiple markets or regions - internationalization or localization.

Remote (Worldwide) — Europe, North America

On-Call Rotation - There would be an on-call rotation for this role as a requirement.
Employees new to Affirm typically come in at the start of the pay range.
Affirm is able to offer visa sponsorship for this role, but do require that someone is based in Spain for the role.

Visa sponsorship available

Affirm is hiring a Senior Software Engineer, Back-end (Fraud)