Backend Engineer
Backend Engineer building product-facing APIs, services, and data systems on top of AI evaluation platforms. Design and ship low-latency APIs, enterprise features (billing, RBAC, multi-tenancy), and data architectures for Leaderboards and Evals. Requires 5+ years backend experience, strong Go and Postgres skills, and product mindset.
About the job
What You'll Do
- Build API-based products from the ground up. Design and ship low-latency, high-reliability APIs and services that power Leaderboards, Evals, and Arena data products.
- Turn evaluations into product. Partner with the research team to take novel eval methods and make them durable, full-featured products: scoring pipelines, data models, and the APIs that expose them.
- Ship enterprise-grade backends. Usage metering, cost attribution, billing integration, authentication, RBAC, multi-tenancy, and audit logging.
- Own the data architecture. Unify public and private evaluation data, design schemas that hold up as the product grows, and make Arena’s data queryable, consistent, and fast.
- Flex across the stack. Contribute to the backend of our Leaderboards and Evals platforms when needed, helping unify our public and private data architectures.
What We're Looking For
- 5+ years of backend engineering experience, with meaningful time spent on building product-facing APIs, services and data systems at scale.
- Strong proficiency in a modern backend language — Go preferred — and the judgment to design APIs other engineers and customers will live with for years.
- Solid data fundamentals. Comfortable modeling, querying, and scaling Postgres; know when to reach for Redis, a queue, or a warehouse.
- Experience composing services into products — integrating payments, auth, analytics, or data pipelines into something coherent and reliable.
- A product-oriented mindset. Think about the developer experience of your APIs, not just the implementation.
- Comfort with ambiguity. Scope is fluid and you’ll wear many hats.
Nice to Have
- Experience with LLM provider APIs (OpenAI, Anthropic, Google, etc.) and the realities of building on them: streaming, token accounting, rate limits, model-specific quirks.
- Background in ML infrastructure, model serving, or evaluation frameworks.
- Experience building enterprise-ready features: SSO, RBAC, audit logs, multi-tenancy.
- Experience building billing and usage infrastructure around systems like Stripe, Metronome, and Orb.
- Familiarity with the modern AI stack (vLLM, LiteLLM, LangChain, etc.).
What we offer
- Competitive compensation and equity aligned to the markets where our team members are based. The base salary range will depend on the candidate’s permanent work location.
- Comprehensive health and wellness benefits, including medical, dental, vision, and additional support programs.
- The opportunity to work on cutting-edge AI with a small, mission-driven team.
- A culture that values transparency, trust, and community impact.
Skills
Go, Postgres, Redis, API Design, RBAC, Multi-Tenancy, Billing Systems, Stripe, LLM APIs, vLLM, Litellm, LangChain
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