Staff Software Engineer, Backend (Cost Engineering)

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.

Engineering owns cost visibility and optimization across Affirm's cloud and AI infrastructure. We're the team that tells the business what it's spending, why it's changing, and what to do about it — from AWS resource waste and tagging strategy to the newer frontier of AI/LLM spend across the company's growing set of AI tools. We treat cost anomalies with the same rigor as production incidents: we've built a severity framework (mirroring Affirm's SEV0–3 incident model but mapped to dollar impact) with defined detection sources, TTD/TTR metrics, and escalation paths, and we operate a clear RACI with partner orgs — we own visibility and alerting, and partner teams own remediation (at times we may dig in deep and own remediation too!), so accountability never gets diffuse.

As a Staff Cost Engineer, you'll operate at the intersection of finance, infrastructure, and data engineering — designing the tooling, automation, and processes that scale cost governance across a fast-growing multi-cloud and multi-AI-vendor footprint. You'll set technical direction for the team, influence cost strategy with infra and platform leaders across the org, and turn ambiguous "why did spend spike" questions into durable systems and self-service tooling. We're a small, high-leverage team — you'll have outsized influence on how Affirm thinks about cost.

What You'll Do · 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, polcities, 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.

What We Look For · You have 8+ years of experience designing, developing and launching backend systems at scale using languages like Python or Kotlin. · You have an extensive track record of developing highly available distributed systems using technologies like AWS, MySQL, Spark and Kubernetes. · Experience with a FinOps or cost-visibility platform (e.g., FinOut, CloudHealth, Kubecost, or an internal equivalent) — building dashboards, anomaly detection, or savings/waste reporting rather than just consuming them. · Track record of building automation or tooling (Python, Terraform, or similar) that turns a manual cost-review process into a scalable, self-service system — not just one-off analysis. · Hands-on experience with cloud billing/cost data at scale (AWS Cost & Usage Reports, Snowflake or similar warehouses) — comfortable writing complex SQL to model spend, allocate cost, and build unit-economics views from raw billing data. · You have 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. · You thrive