Senior Software Engineer, Backend (AI Platform)

The AI Platform team owns Affirm's paved path for building, running, evaluating, and governing AI systems. As a team, we are responsible for building and exposing simple, governed interfaces to models, tools, and agents, with identity, cost attribution, reliability, and security built in. Examples of components include the LLM Gateway, the MCP Gateway, the Agent Runtime, and the evals and observability layer.

Responsibilities

Plan, execute, and own technical decisions and projects within the AI Platform team, from design through launch and on-call; Design and build the gateway, runtime, and evaluation services that take AI workloads from pilot to production, securely scaling across millions of users and their transactions; Make AI spend attributable and governable by building identity, quota, routing, caching, and failover controls; Partner with security, infrastructure, and product engineering teams to set guardrails for agentic workloads and the on-behalf-of identity model for tool access; Create and monitor metrics for team systems and own operational health: monitoring, alerting, runbooks, and on-call; Set and improve code review and design standards, and advocate for them through writing and tech talks; Use AI tools and agentic workflows daily as a multiplier for code, design review, and operations; Educate, mentor, and grow engineers in the team, and drive best practices around design, coding, and testing

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; Practical experience building with LLMs, agents, or AI frameworks in production (inference APIs, LLM gateways such as LiteLLM or similar, MCP, tool calling, evals, or agent runtimes); Understanding of AI usage and the infrastructure needed to support AI workloads across disciplines; Experience defining a technical plan for the delivery of a significant feature or system component with an elegant, simple and extensible design; Writes high quality code that is easily understood and used by others; Proficient at making significant changes in a large code base, with tools and practices to do so safely; Takes ownership of growth and proactively seeks feedback from team, manager and stakeholders; Strong verbal and written communication skills for collaboration with a global engineering team; Equivalent practical experience or a Bachelor's degree in a related field; Remote role open only to candidates residing in Alberta, British Columbia, Manitoba, New Brunswick, Newfoundland and Labrador, Nova Scotia, Ontario, Prince Edward Island, or Saskatchewan

Benefits

100% subsidized medical coverage, dental and vision for employee and dependents; Monthly stipends for health, wellness and tech spending; Equity rewards; Flexible time off and generous holiday calendars; Employee stock purchase plan (ESPP) with discount; Remote-first work with flexibility; All new hires invited to an in-person onboarding experience