Senior Back-End Engineer, Remote — Real-Time Fraud

Affirm; Spain (TX); Hybrid; USD 81,000 - 138,000; Full time

Benefits offered by this job

Visa sponsorship for Spain

Health and wellness benefits

Job summary

Affirm is a remote-first fintech company building fraud decisioning systems to protect buyers and merchants. We are seeking a Senior Software Engineer to design real-time fraud decisioning services in Python or Kotlin, extend the system to new markets, and collaborate with teams across North America.

You will build the platform for market-by-market launches, integrate region-specific vendors, and support AI-powered signals while maintaining high reliability.

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 a track record of delivering maintainable, extensible services.
• Fluency with AI-driven engineering - directing and reviewing AI-generated code and ensuring 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 in distributed teams.
• Proactive, ownership-driven mindset with a focus on learning and team success.
• Nice-to-have: experience with Snowflake, dbt, Airflow, Chronosphere; internationalization or localization; fintech risk or real-time decisioning.

Responsibilities

• Own and deliver quarterly goals for your team and mentor engineers.
• Design and implement real-time fraud decisioning services and APIs in Python or Kotlin.
• Extend the Fraud Decisioning System to markets beyond the US.
• Build a scalable platform to launch fraud decisioning in new countries quickly.
• Integrate region-specific risk vendors and operationalize AI signals for real-time decisioning.
• Collaborate with Product, ML, Analytics, and Fraud Strategy across the lifecycle.
• Maintain systems with metrics, on-call readiness, and incident response.
• Foster quality and ownership through code reviews and mentorship.
• Participate in on-call rotation.

Skills

Python

Kotlin

Distributed systems

SQL

Tools

AWS

MySQL

PostgreSQL

Kubernetes

Snowflake

dbt

Airflow

Chronosphere

Job description

Affirm is a remote-first fintech company building fraud decisioning systems to protect buyers and merchants. We are seeking a Senior Software Engineer to design real-time fraud decisioning services in Python or Kotlin, extend the system to new markets, and collaborate with teams across North America.

You will build the platform for market-by-market launches, integrate region-specific vendors, and support AI-powered signals while maintaining high reliability.