Founding Engineer

ABOUT THE ROLE Join a small engineering team at an early-stage ad technology company to build and evolve the systems that decide which ads reach users in real time. You will own work across data pipelines, machine learning, and production serving, with direct impact on the recommendation system and its business outcomes. WHAT YOU'LL DO - Design and ship low-latency ad retrieval, ranking, and reranking systems that balance advertiser performance with user experience. - Build data pipelines and feature infrastructure to train models using reward signals that arrive on different timelines, from clicks to conversions. - Develop user and context representations from conversational data, engagement history, and signals such as device, location, and session context. - Build serving infrastructure designed for sub-second response times and cost efficiency. - Create generative agents that produce playable and video ad variations, and feed their performance back into the recommendation system. WHAT WE'RE LOOKING FOR - Experience level: 0 to 3 years, with at least one ML or AI system shipped to production. - End-to-end experience with backend systems, data pipelines, model training, and production serving, ideally including a recommendation or ranking system. - Strong systems fundamentals and the ability to reason from first principles across infrastructure for large user volumes, classical machine learning, and AI agents. - Experience with PyTorch is relevant; AdTech or recommendation systems experience is a plus. - An active GitHub or shipped side projects demonstrating work across backend, ML, or infrastructure. - Interest in games and playable ad formats is valued. Startup experience, mentoring, or experience building AI-native products is also relevant. - Must be a US citizen or green card holder and able to work on-site in San Francisco five days per week. COMPENSATION & BENEFITS Base salary is $200,000 to $250,000 annually, with equity. Visa sponsorship is not available. LOCATION On-site in San Francisco, California, United States, five days per week.