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.