Backend Engineer

Backend Engineer (OpenAI API) $200,000 - $250,000 + Equity + Benefits + 401(k) On-site in San Francisco, CA Are you a backend engineer who takes pride in building clean, provider-agnostic systems at scale? Do you care deeply about developer experience, building interfaces that millions of users will interact with through a Python SDK, rather than just making something technically work? This is an opportunity to join a fast-growing, profitable startup at the forefront of AI infrastructure, building the compliance and reliability layer that enterprise customers like Adobe, Netflix, and NASA depend on in production. Backed by top-tier investors, the team has built the world's most widely used LLM Gateway, a unified platform that gives developers secure, scalable access to every major LLM provider. Now, they're building their second product, and looking for an AI Engineer to ensure the platform unifies the format for calling LLM APIs across the OpenAI and Anthropic spec. As an early engineering hire, you'll work directly with the CEO and CTO on writing transformations that convert API requests across provider formats, building provider-agnostic unification functionality, and maintaining an excellent LLM interoperability layer across LLMs, MCPs, and Agents. If you're looking for a role where your engineering work is used directly by thousands of engineering teams around the world, with real ownership over product decisions and not just implementation, this is an outstanding opportunity. The Role Write transformations converting API requests from OpenAI/Anthropic spec to various LLM provider formatsBuild provider-agnostic unification functionality, including session management across non-OpenAI modelsDesign systems supporting provider-level features at the gateway level (skills, compaction, batches)Support a wide range of MCP Auth flows and enable various Agent use-casesShape developer experience for millions of users via the Python SDK The Person 1+ years of backend or full-stack experience with production systemsExperience working with the OpenAI API, understands the nuances between /chat/completions and /responsesEager to talk to users and help solve real problemsCS degree or equivalent from a top 30 program in the US or Canada