Senior Infrastructure Engineer

About the Role

LMArena is seeking a Senior Infrastructure Engineer to define, build, and evolve the technical foundations that power the world’s most transparent AI evaluation platform. This is not just an architecture role - you’ll partner directly with product, security, and data teams to identify bottlenecks, design resilient systems, and ship the code that keeps our platform fast, reliable, and secure at scale.

You’ll have a broad impact across the stack: optimizing performance, building primitives that accelerate feature delivery, hardening our systems against abuse, and scaling infrastructure to handle billions of API requests and real-time votes. If you love working across boundaries, getting deep into code, and making infrastructure a product in its own right, this is the role for you.

Responsibilities

• Own technical strategy for LMArena’s core infrastructure - networking, APIs, services, data systems, and security foundations.
  

• Design and implement high-performance systems that scale to hundreds of millions of real-time interactions and evaluations per day.
  

• Collaborate with security engineering to embed anti-abuse measures, Sybil resistance, and trust systems into core platform architecture.
  

• Partner with product engineering to deliver infrastructure improvements that directly accelerate feature velocity and reliability.
  

• Build developer-facing primitives and tooling—internal APIs, SDKs, CI/CD enhancements—that make our platform more productive and safe to build on.
  

• Monitor, profile, and optimize system performance across backend services, databases, and networking layers.
  

• Drive operational excellence through observability, capacity planning, and incident response best practices.
  

• Mentor engineers across the company in building scalable, performant, and secure systems.
  

Who is LMArena?

Created by researchers from UC Berkeley’s SkyLab, LMArena is an open platform where anyone can access, explore, and interact with the world’s leading AI models. By comparing them side by side and casting votes, the community shapes a public leaderboard, making AI progress more transparent and grounded in real-world usage.

Trusted by Google, OpenAI, Meta, xAI, and more, LMArena is rapidly becoming essential infrastructure for human-centered AI evaluation at scale. With over one million monthly users and growing developer adoption, your work will influence the next generation of safe, aligned AI systems.

Requirements

• 8+ years of experience in backend, infrastructure, or systems engineering, including staff-level scope in a high-scale production environment.
  

• Proven experience designing and operating distributed systems at scale (millions of DAU / billions of requests).
  

• Deep knowledge of networking fundamentals, service-to-service communication, and traffic routing at scale.
  

• Hands-on experience with performance profiling, observability, and reliability engineering.
  

• Track record of collaborating with security and product engineering to deliver both foundational systems and user-facing features.
  

• Clear communicator who can lead technical discussions, build alignment across teams, and partner with us to prioritize the needs of the business.
  

Bonus Points

• Experience with Node.js, Typescript, Serverless Environments, Postgres
  

• Background in anti-abuse systems, security engineering, or trust & safety platforms.
  

• Experience building infrastructure for real-time, user-driven platforms.