Staff Software Engineer, Backend (Capacity Modeling)

Affirm is reinventing credit to make it more honest and friendly, giving consumers the flexibility to buy now and pay later without any hidden fees or compounding interest. The Capacity Modeling team ensures Affirm can safely handle forecasted traffic—especially during peak sales events—by translating demand forecasts into concrete, testable capacity plans. You will design and maintain statistical capacity models that map traffic inputs to resource outputs and convert those forecasts into recommended infrastructure settings across regions and environments.

About the Role

As a Staff Software Engineer on the Capacity Modeling team, you will set technical strategy on a year-long time scale and drive critical, business-impacting projects. You will work across product development by collaborating with product management, design, and analytics to ensure technical sustainability and manage risks and trade-offs. The team focuses on capacity planning for compute and infrastructure resources including ElasticCache, DynamoDB, and AuroraDB.

Responsibilities

• Define and advocate for technical solutions and operational processes that multiply team effectiveness
• Own your team's operations and availability by establishing monitoring, triage rotations, playbooks, policies, testing, and alerting for on-call support
• Foster a culture of quality and ownership by setting code review and design standards, and advocating for them through writing and technical talks
• Develop talent on your team through feedback, guidance, and leading by example
• Design and maintain statistical capacity models that translate traffic forecasts into resource allocation recommendations (pod counts, HPA ranges, infrastructure sizing)

Requirements

• 8+ years of experience designing, developing, and launching backend systems at scale using Python or Kotlin
• Extensive track record developing highly available distributed systems with AWS, MySQL, Spark, and Kubernetes
• Experience supporting capacity scaling for large-scale sales events (Prime Day, Black Friday Cyber Monday, or similar)
• Proficiency tuning autoscaling, CPU/Memory, and multi-threading for compute-type workloads
• Track record delivering major features, system components, or deprecating existing functionality through technical and execution planning
• Ability to write high-quality, easily understood code
• Comfort with ambiguity and complex technical challenges

Benefits

• Remote position based in Canada