Backend Engineer

Arena Intelligence, Inc. • Bay Area, CA

7d

About The Position

Arena Intelligence is looking for a backend engineer to build the products and platforms that sit on top of our evaluation systems - the APIs, services, and data systems that turn Arena’s evals into products that enterprises depend on.
This is the application layer of the Arena Service. Where our infrastructure teams builds the gateways and runtimes beneath - you will work closely with them to build the backends that customers will touch directly. This will include the APIs that expose Arena and enterprise data and the systems that manage usage, billing and multi tenant access. This work spans product surfaces of varying maturity and the data pipelines behind them - zero to one in places and scale-it up in others.
You'll be an early member of our enterprise team, working closely with infrastructure engineers, researchers, and product leadership. We move fast and stay rigorous.

Requirements

• 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. You’re comfortable modeling, querying, and scaling Postgres, and you 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. You think about the developer experience of your APIs, not just the implementation. You ask “why” before “how.”
• Comfort with ambiguity. We’re a startup. Scope is fluid, context shifts, and you’ll wear many hats. That should sound exciting, not stressful.

Nice To Haves

• 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.).

Responsibilities

• Build API-based products from the ground up. Design and ship the low-latency, high-reliability APIs and services that power Leaderboards, Evals, and Arena data products — clean, versioned, and built for the developers who consume them.
• 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 — the systems enterprise customers expect.
• Own the data architecture. Unify our 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.

Benefits

• Competitive compensation and equity aligned to the markets where our team members are based.
• 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

What This Job Offers

• Job Type: Full-time
• Career Level: Senior
• Education Level: No Education Listed