Staff Software Engineer, Backend (Capacity Modeling)

About the Role

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. They build and maintain statistical capacity models that map traffic inputs (e.g., checkout volume, app opens, batch/job activity) to resource outputs (CPU, memory, connections) and then convert those forecasts into recommended capacity settings such as pod counts, HPA ranges, and/or infrastructure sizing changes across regions and environments.

The coverage of infrastructure resources includes Compute and infrastructure such as ElastiCache, DynamoDB, AuroraDB, and more.

What You'll Do

• Responsible for setting technical strategy for your team on a year-long time scale, tying it together with critical, business-impacting projects.
• Collaborate across teams in the product development lifecycle with product management, design, and analytics to ensure technical sustainability, risks, and trade-offs are well understood and managed.
• Act as a force-multiplier for your team through definition and advocacy of technical solutions and operational processes.
• Take ownership of team operations and availability by ensuring appropriate monitoring, triage rotations, playbooks, policies, testing, and alerting are in place to support "keep the lights on" and on-call efforts.
• Foster a culture of quality and ownership by setting code review and design standards, advocating for them through writing and tech talks.
• Develop talent on the team by providing feedback, guidance, and leading by example.

What We Look For

• 8+ years of experience designing, developing, and launching backend systems at scale using languages like Python or Kotlin.
• Extensive track record of developing highly available distributed systems using technologies like AWS, MySQL, Spark, and Kubernetes.
• Experience supporting scale up and down of large-scale sales events such as Prime Day, Black Friday Cyber Monday, or other sales holidays.
• Experience tuning autoscaling, CPU/Memory, and multi-threading for compute-type workloads.
• Experience delivering major features, system components, or deprecating existing functionality through the definition of a technical and execution plan.
• Ability to thrive in ambiguity, moving from low-level language idioms to large system architecture.
• Demonstrated growth and impact trajectory gathering and iterating on peer and cross-functional feedback.
• Strong verbal and written communication skills.
• Equivalent practical experience or a Bachelor's degree in a related field.