Senior Software Engineer (Comms Core)

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. About the Engineering team The Engineering team builds systems that power Affirm’s mission. We take pride in our craft, building reliable, performant, and scalable solutions that touch every part of the business. Whether we’re enabling new ways to pay, ensuring our platforms can scale to the most demanding levels in the industry, or developing seamless servicing experiences, our focus is on solving complex problems through exceptional engineering. About the team Affirm’s Communications team builds and modernizes the highly available platform that delivers billions of customer messages reliably and on time across the customer journey. As a senior backend engineer, you will shape multi-region, multi-tenant infrastructure, APIs, and vendor integrations that help product teams communicate with customers at scale. What you’ll do • You will own and deliver quarterly technical goals for the Communications area, collaborating with teammates to solve ambiguous, open-ended problems across messaging infrastructure. • You will design and evolve reliable backend services for high-volume communications across multi-region, multi-tenant environments, including orchestration, delivery, preferences, templates, and observability. • You will collaborate with product management, design, analytics, security, and engineering partners throughout the product lifecycle, articulating technical constraints and balancing customer impact, risks, and trade-offs. • You will design, implement, and operate resilient integrations with external messaging vendors, balancing reliability, latency, cost, and compliance. • You will proactively identify and solve project, process, technology, or business issues that affect scalability, developer experience, and operational resilience. • You will support the operations and availability of your team’s services by defining service-level objectives and metrics, improving alerting and incident response, and participating in on-call efforts. • You will foster quality and ownership by improving design, testing, code review, rollout, and operational standards, and advocating for them through writing and tech talks. • You will help develop talent on your team by providing feedback, mentorship, and technical direction, and leading by example. • On-Call Rotation - There would be an on-call rotation for this role as a requirement. What we look for • You have 5+ years of experience in software development or engineering, with a deep understanding of system design and architecture. • Proficiency in modern programming languages such as Python, Kotlin, or similar. • You have a track record of developing highly available distributed systems using technologies like AWS, MySQL, DynamoDB, and Kubernetes. • You have experience designing multi-region, multi-tenant platforms with strong isolation, scalability, failure recovery, and data-consistency guarantees. • You have experience integrating with third-party communications or messaging vendors and designing abstractions that account for different capabilities, rate limits, and failure modes. • You have experience defining a technical plan for the delivery of a significant feature or system component with an elegant, simple and extensible design. You write high quality code that is easily understood and used by others. • You are proficient at making significant changes in a large code base, and have developed a suite of tools and practices that enable you and your team to do so safely. • You are proficient with AI-assisted development tools and apply sound judgment to validate their outputs. •