Infrastructure Engineer, TL

Arena Intelligence is looking for an engineer to build the core infrastructure that sits beneath our online evaluation systems — the AI gateways, automated arena runtimes, and serving layers that make real-world model evaluation possible at scale.

This is a critical part of the Arena Service. Arenas are live, online systems: they route traffic across frontier models from many providers, handle bursty and unpredictable load, need to fail gracefully when upstream models do, and have to remain fair and consistent under all of it. We exist to build foundational infrastructure for our users that scales, is reliable, and makes the complexities of operating this infrastructure at scale disappear. We need a practitioner who's shipped this kind of infrastructure before and knows where the sharp edges are.

You'll be an early member of our infrastructure team, working closely with researchers, engineers, and product leadership. The work is zero-to-one in places and scale-it-up in others. We move fast and stay rigorous.

Build API-based products from the ground up. Design and implement low-latency, high-reliability APIs for leaderboards, models, and arenas.

Solve hard streaming problems. Handle SSE/streaming responses across heterogeneous providers, including partial failure recovery, mid-stream fallback, and consistent response normalization.

Ship enterprise-grade infrastructure. Build the systems enterprise customers expect: rate limiting, authentication, usage metering, cost attribution, audit logging, and SOC 2 compliance.

Build deep observability. Instrument infrastructure with distributed tracing, latency breakdowns, token-level usage tracking, and real-time dashboards so customers (and we) can see exactly what's happening.

Build AI-centered products. Integrate with our core evaluation platform, Arena data, and customer-specific benchmarks. Collaborate with the research team to turn novel ideas into full-featured products.

Flex across the stack. Contribute to the backend of our Leaderboards and Evals platforms when needed, helping unify our public and private data architectures.

4+ years of backend engineering experience, with meaningful time spent on distributed systems, infrastructure, or developer-facing platforms.

Strong proficiency in Go and/or Rust, with hands-on experience building high-throughput APIs or proxy/gateway systems.

Experience with LLM provider APIs (OpenAI, Anthropic, Google, etc.) and a working understanding of the challenges: streaming, token management, rate limits, model-specific quirks.

Solid cloud infrastructure skills — you're comfortable with AWS or GCP, Kubernetes, Terraform, and database systems like Postgres and Redis.

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.

Experience building API gateways, proxies, or developer tools (Bifrost, Kong, Envoy, Tyk, or custom).

Background in ML infrastructure, model serving, or evaluation frameworks.

Experience building enterprise-ready features: SSO, RBAC, audit logs, multi-tenancy.

Experience building billing infrastructure around systems like Stripe, Metronome and Orb

Familiarity with the modern AI infra stack (vLLM, LiteLLM, LangChain, etc.).