Senior Software Engineer, Full Stack

About the Role:

LMArena is seeking a Senior Full-Stack Product Engineer to lead the technical design and development of AI-focused products across our platform. You’ll be responsible for owning features end-to-end—from proposing technical approaches and implementing core product flows, to deploying new functionality and tracking its impact. This role is ideal for someone with proven experience building reliable business logic at scale who is excited to shape how people interact with cutting-edge AI models.

Responsibilities:

• Expand data structures and business logic to support new features
• Visualize feature performance and usage metrics through internal tooling and dashboards
• Own the full feature lifecycle—from technical scoping to deployment and iteration based on insights
• Identify and advocate for process improvements in development, testing, and deployment.
• Experiment with new tools and frameworks to enhance productivity and product capabilities

Who is LMArena?

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

Why Join Us?

Trusted by organizations like Google, OpenAI, Meta, xAI, and more, LMArena is rapidly becoming essential infrastructure for transparent, human-centered AI evaluation at scale. With over one million monthly users and growing developer adoption, our impact is helping guide the next generation of safe, aligned AI systems—grounded in open access and collective feedback.

Our work is regularly referenced by industry leaders pushing the frontier of safe and reliable AI. Sundar Pichai, Jeff Dean, Elon Musk, and Sam Altman.

• High Impact: Your work will be used daily by the world’s most advanced AI labs.
• Global Reach: Develop data infrastructure powering millions of real-world evaluations, influencing AI reliability across industries at the top-tier
• Exceptional Team: We are a small team of top talent from Google, DeepMind, Discord, Vercel, UC Berkeley, and Stanford.

Requirements:

• 5+ years of experience in software engineering, with a focus on full-stack or backend product development
• Deep knowledge in SQL and managing databases at scale
• Familiarity with testing practices and tools like Vitest (or similar testing frameworks)
• Clear communicator and strong collaborator across design, product, and engineering teams
• Bonus: PowerUser Experience with Supabase or Vercel's ai sdk

Our Tech Stack:

• NextJS
• Tailwind
• ShadCN
• HonoJS
• Postgres
• Vitest

What we offer:

• 210k - 231k + equity. Actual compensation will depend on job-related knowledge, skills, experience, and candidate location.
• Competitive salary and meaningful equity
• Comprehensive healthcare coverage (medical, dental, vision)
• The opportunity to work on cutting-edge AI with a small, mission-driven team
• A culture that values transparency, trust, and community impact

Come help build the space where anyone can explore and help shape the future of AI.