Staff Software Engineer, Backend (Capacity Modeling)

About the Position

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.

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.

Responsibilities

• You will be responsible for setting technical strategy for your team on a year-long time scale, and help your team tie it together with critical, business-impacting projects.
• You will collaborate 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.
• You will act as a force-multiplier for your team through your definition and advocacy of technical solutions and operational processes.
• You take 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.
• You will foster 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.
• You will help develop talent on your team by providing feedback and guidance, and leading by example.

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 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 in a system through the definition of a technical and execution plan. You 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.
• Demonstrated mastery of 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.
• Either equivalent practical experience or a Bachelor’s degree in a related field.

We Offer

• Competitive salary: USA base pay range (CA, WA, NY, NJ, CT) per year: $230,000 - $290,000; USA base pay range (all other U.S. states) per year: $204,000 - $264,000.
• Health coverage at no cost: We cover 100% of premiums for employees and their dependents.
• Spending stipends: Monthly stipends support your tech setup, and the ability to choose health and wellness options that are right for you.
• Time off to recharge: Flexible time off and generous holiday calendars help you rest when you need to.
• Own a piece of what you build: Our employee stock purchase plan (ESPP) lets you buy Affirm stock at a discount.

About the Company

Affirm is proud to be a remote-first company. Most roles can be done from almost anywhere within the country of employment. Some positions may occasionally require in-person work at an Affirm office, and a few are office-based due to the nature of the work. All new hires will be invited to attend an in-person onboarding experience.

We’re committed to providing an inclusive interview process, including accommodations for candidates with disabilities. If you need support, we’re happy to help.

For positions based in San Francisco or Los Angeles: Affirm considers qualified applicants with arrest and conviction records, as required by law.

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