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Salary: CAD 153,000 - 213,000 / annual
Affirm is hiring a Senior Software Engineer, Backend (Cost Engineering) to lead the Capacity Modeling team. This team ensures Affirm can safely handle forecasted traffic—especially during peak sales events—by translating demand forecasts into concrete, testable capacity plans. The team builds and maintains statistical capacity models that map traffic inputs (e.g., checkout volume, app opens, batch/job activity) to resource outputs (CPU, memory, connections) and converts those forecasts into recommended capacity settings such as pod counts, HPA ranges, and infrastructure sizing changes across regions and environments.
In this role, you will own and deliver quarterly goals for your team, leading engineers through ambiguity to solve open-ended problems while ensuring everyone is supported throughout delivery. You will collaborate with product management, design, and analytics by participating in ideation, articulating technical constraints, and partnering on decisions that properly consider risks and trade-offs. You will proactively identify project, process, technology, or business issues, advocate for them, and lead in solving them.
You will support the operations and availability of your team's artifacts by creating and monitoring metrics, escalating when needed, and supporting "keep the lights on" and on-call efforts. You will foster a culture of quality and ownership on your team by setting or improving code review and design standards, and advocating for them beyond your team through writing and tech talks. You will help develop talent on your team by providing feedback and guidance, and leading by example.
Affirm is a remote-first company. Most roles can be done from almost anywhere within Canada. New hires will be invited to attend an in-person onboarding experience. Benefits include 100% subsidized medical, dental, and vision coverage for you and dependents; monthly stipends for health, wellness, and tech spending; flexible time off; and an employee stock purchase plan.
REQUIREMENTS:
- 4+ years of experience designing, developing, and launching backend systems at scale using languages like Python or Kotlin
- Track record of developing highly available distributed systems using technologies like AWS, MySQL, and Kubernetes
- Experience supporting scale-up and scale-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 defining a technical plan for the delivery of a significant feature or system component with an elegant, simple, and extensible design; ability to write high-quality code that is easily understood and used by others
- Proficiency at making significant changes in a large code base, with a suite of tools and practices that enable safe changes
- Demonstrated ownership of your growth, proactively seeking feedback from team, manager, and stakeholders
- Strong verbal and written communication skills supporting effective collaboration with global engineering team
- Bachelor's degree in a related field or equivalent practical experience
