Senior Software Engineer

At Affirm, we exist for the moments that matter—giving people a clear, predictable way to pay over time, with no hidden fees, no surprises, and no tradeoffs on what matters most.

The Card Loan Platform team builds the high-throughput decision engine at the heart of Affirm’s card products. Unlike traditional cards, every pay-later transaction is backed by its own unique loan, and our system is the "invisible piping" that makes this complex model work at scale. Every swipe triggers our platform to solve a hard problem in milliseconds: matching messy, fragmented payment network data to the correct loan to drive real-time approvals, origination, and refunds.

As Affirm experiences explosive growth, our team's contributions are a key enabler. This isn't just another backend role; you'll be building the "financial brain" for our flagship card products, with your work on the critical path for every single swipe. We're tackling a unique, high-stakes distributed systems challenge that demands exceptional correctness and massive scale. You will partner closely with product, data science, and engineering teams to design and build the future of our industry-leading money movement platform.

If you are passionate about making foundational design decisions and building a beloved, lasting financial brand—come join us. It’s going to be an amazing ride!

What you'll do

• Drive technical strategy by leading the planning, prioritization, and execution of projects, ensuring alignment with product, technical, and business goals.
• Lead the end-to-end system design and development of large-scale, high-availability services. This includes building robust APIs and data models for our micro-service and event-driven architectures.
• Collaborate across functions with partners in Product, Analytics, Design, Legal, and Accounting and to define requirements and execute our card loan attribution and lifecycle strategy.
• Ensure system health and performance by analyzing and troubleshooting complex technical issues, optimizing existing code, and driving solutions that focus on long-term robustness and scalability.
• Mentor and grow the team by guiding junior engineers, leading technical discussions and design reviews, and championing best practices through code review.

What we look for

• 5+ years of experience in software development or engineering, with a deep understanding of system design and architecture.
• Motivated leader, inspiring team growth and fostering a culture of continuous learning
• Excellent communicator, adept at sharing complex ideas with diverse audiences.
• Strong analytical and problem-solving skills, with a creative and solution-oriented mindset.
• Proficiency in modern programming languages such as Python, Kotlin, or simil