Staff Software Engineer, Backend (Capacity Modeling)

Affirm

2d•Remote

About The Position

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. 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 not only Compute but also infrastructure such as ElasticCache, DynamoDB, AuroraDB, and more.

Requirements

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 event such as Prime Day, Black Friday Cyber Monday, or other sales holidays.
Tuned autoscaling, CPU/Memory, and multi-threading for compute type workloads.
Experience delivering major features, system components or deprecating existing functionality in a system through the definition of a technical and execution plan.
Write high quality code that is easily understood and used by others.
Thrive in ambiguity, and are comfortable moving from low level language idioms all the way to the architecture of large systems to understand how they work.
Growth and impact trajectory demonstrates that you have mastered gathering and iterating on feedback from your engineering and cross-functional peers.
Strong verbal and written communication skills that support effective collaboration with our global engineering team.
Equivalent practical experience or a Bachelor’s degree in a related field.

Responsibilities

Setting technical strategy for your team on a year-long time scale, and help your team tie it together with critical, business-impacting projects.
Collaborating across teams in the product development lifecycle by collaborating with product management, design & analytics to ensure technical sustainability, risks and trade-offs are well understood and managed.
Acting as a force-multiplier for your team through your definition and advocacy of technical solutions and operational processes.
Taking ownership of your team’s operations and availability by ensuring you have the right monitoring, triage rotations, playbooks, policies, testing and alerting in place to support “keep the lights on” & on-call efforts.
Fostering a culture of quality and ownership on your team by setting code review and design standards for your team, and advocating for them beyond your team through your writing and tech talks.
Helping develop talent on your team by providing feedback and guidance, and leading by example.