Founding Software Engineer

Founding Software Engineer (AI Evaluation Infrastructure)

Location : San Francisco, CA (FiDi)

Employment Type : Full-time

Work Arrangement : On-site (6 days a week in office)

About the Role

Our client, is a high-growth AI startup that is building the most complex infrastructure for frontier data creation and evaluation for LLMs and AI Agents. They work with all five of the leading AI labs and top-tier YC companies, reflecting their sharp growth rate and talent density. The company is backed by $3 million in funding and features a founding team from rigorous environments like Citadel Securities, Google, and Meta.

They are seeking a Founding Software Engineer for a high-impact, non-narrow role with end-to-end ownership . You will operate across the full stack and infrastructure, contributing directly to systems that push the frontier of AI evaluation.

What You’ll Do

• Design and build scalable systems : This includes RL (Reinforcement Learning) environments, core APIs, and human-in-the-loop platforms.
• Tackle diverse projects : One week you might prototype a new RL environment from a research paper; the next, you'll deploy distributed experiments on Kubernetes ; the week after, you might improve Next.js dashboards or build a Kafka pipeline for analytics.
• Lead an initial core project : Design and scale the AI interviewer platform to handle tens of thousands of interviews monthly.
• Contribute to core infrastructure powering data and evaluation for leading AI labs.
• Write clean, maintainable code, participate in code reviews, and solve real-world scalability and reliability challenges.
• Collaborate quickly across research, product, and design teams.
• 0-3 years of experience as a full-stack Software Engineer . (The company is flexible for very strong backgrounds).
• Demonstrated passion for taking on end-to-end ownership and thriving in a fast-paced, high-intensity environment.
• Salary : $120K - $200K (Flexible for a very strong background)
• Equity : 0.5% to 1%
• Visa Sponsorship : Available
• Benefits include : Health insurance, daily lunch & dinner covered, and a free gym membership.

Due to the high volume of applications we anticipate, we regret that we are unable to provide individual feedback to all candidates. If you do not hear back from us within 4 weeks of your application, please assume that you have not been successful on this occasion. We genuinely appreciate your interest and wish you the best in your job search.

Commitment to Equality and Accessibility :

At MLabs, we are committed to offer equal opportunities to all candidates. We ensure no discrimination, accessible job adverts, and providing information in accessible formats. Our goal is to foster a diverse, inclusive workplace with equal opportunities for all. If you need any reasonable adjustments during any part of the hiring process or you would like to see the job-advert in an accessible format please let us know at the earliest opportunity by emailinghuman-resources@mlabs.city.

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