← All roles

Senior Software Engineer, Back-end (Fraud)

Affirm· Checkout
Apply on company site
Hybrid (Poland)PLN 308k - PLN 428kfull-timePosted 3mo ago

About the role

Senior backend engineer role focused on real-time fraud decisioning systems, regional expansion (Canada, UK, Australia), and building scalable services to enable Affirm’s Fraud Decisioning System across markets.

Responsibilities

  • Own and deliver quarterly goals for your team, guiding engineers through ambiguity to solve open-ended problems and supporting delivery.
  • 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 platform and tooling to launch fraud decisioning in new countries quickly, turning market setup into a repeatable process.
  • Integrate region-specific fraud and risk vendors and operationalize ML/AI signals powering real-time decisioning; utilize AI tooling to accelerate engineering.
  • Support peers and stakeholders across the product lifecycle, articulating technical constraints and balancing risks and trade-offs.
  • Maintain operations and availability of team systems by creating/monitoring metrics, escalating issues, and contributing to on-call efforts.
  • Foster a culture of quality and ownership by setting/designing code review standards, mentoring teammates, and leading by example.

Qualifications

  • 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 track record of delivering maintainable, extensible services
  • Fluency with AI-driven engineering and familiarity with tools like Claude Code; ability to direct and review AI-generated code for correctness, quality, and security
  • 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
  • Proactive, ownership-driven mindset with a focus on learning and team success
  • Nice to have: Experience with Snowflake, dbt, Airflow, Chronosphere
  • Nice to have: Background in fraud prevention, risk systems, or real-time decisioning
  • Nice to have: Experience building for multiple markets or regions (internationalization/localization)
  • Nice to have: Fintech or highly regulated environment experience regarding risk, compliance, and operations

Skills

Required:Backend development (Python or Kotlin)Distributed systemsAWSMySQL/PostgreSQLKubernetesSQLCI/CDAI-driven engineeringCommunication

Benefits

  • Competitive paid time off, paid holidays, and additional Away Days
  • Comprehensive private healthcare through Lux Med’s Platinum package
  • MultiSport card for health and well-being
  • Learning and development programs
  • Family healthcare support through Maven and parental leave support through Parentaly
  • Mental well-being support through Lyra (up to 12 confidential counseling/coaching sessions per year)
  • Financial well-being support through Northstar with unlimited access to Certified
  • Financial Advisors and planning tools at no cost
  • Employee Resource Groups (ERGs)
  • Eligibility for creative tax benefits, subject to law and policy
  • Flexible spending wallets for technology and wellbeing needs (rebate up to 1390 zł/month)
Last updated Sep 16, 2026. Interested? Apply on the company site.

About Affirm

Pay over time with flexible payment plans and no fees

Buy now pay later without the fees. Flexible payment options with longer plans, lower payments, and no fees. Pay in 4 interest-free or get more time and see your total cost upfront.

Buy now pay laterFinancial servicesPayment plansCredit
Company profileWebsite

More open roles at Affirm