Senior Software Engineer, Back-end (Fraud)

Stack

Responsibilities

• ▹Own and deliver quarterly goals for the team, leading engineers through ambiguity
• ▹Design and implement real-time fraud decisioning services and APIs in Python or Kotlin, extending the 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 and safely
• ▹Integrate region-specific fraud and risk vendors, help operationalize ML/AI signals, use modern AI tooling to move faster
• ▹Collaborate with Product, Machine Learning, Analytics and Fraud Strategy across the product development lifecycle
• ▹Support operations and availability of team systems, monitor metrics, contribute to on-call
• ▹Foster a culture of quality and ownership, improve code review/design standards, mentor teammates

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
• ▹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 critically reviewing AI-generated code 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 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 real-time decisioning
• ▹Experience building for multiple markets or regions — internationalization or localization
• ▹Experience in fintech or other highly regulated environments, with understanding of risk, compliance and operational constraints

Soft skills

What we offer

• ▹Base pay: 308,000–428,000 zł/year (Poland)
• ▹Monthly stipends for health, wellness and tech spending
• ▹100% subsidized medical, dental and vision coverage for employee and dependents
• ▹Equity rewards
• ▹Flexible Spending Wallets (tech, food, lifestyle)
• ▹Away Days – wellness days off
• ▹Learning & Development programs
• ▹Parental benefits
• ▹Employee Resource & Community Groups
• ▹Creative tax benefits where applicable
• ▹Remote-first with competitive vacation and holiday schedule

About the company

Affirm is reinventing credit to make it more honest and friendly, giving consumers flexible buy-now-pay-later options without hidden fees or compounding interest. A remote-first company improving the financial lives of 20M+ people.