Senior AI Engineer I

Join a team of brilliant, passionate innovators determined to transform healthcare. At BillionToOne, we've built a category-defining, publicly traded company on Nasdaq where transparency fuels trust, collaboration drives breakthroughs, and every contribution moves the needle on our mission to make life-changing diagnostics accessible to all. We don't just aim for incremental improvements; we build products that are 10x better than anything that exists today.

Our scientists, engineers, sales executives, and visionaries are united by an unwavering commitment to changing the standard of care in prenatal and cancer diagnostics. This is where cutting-edge science meets human compassion, and every innovation you contribute helps remove the fear of the unknown from some of life's most critical medical moments.

If you're driven by purpose, energized by innovation, and ready to help shape the future of precision medicine at scale, this is where you belong.

As BillionToOne scales rapidly, we are building a world-class Commercial Data & Applied AI team. We are currently seeking a highly motivated Senior AI Engineer I to support the design and implementation of AI and automation solutions that optimize operations across our commercial, billing, and customer experience teams.

This is a full-time senior role for engineers excited about applying LLMs, AI, and automation to real-world business challenges in healthcare. You will have the opportunity to join a new team and help shape the vision and culture. You will collaborate cross-functionally with stakeholders in Sales, Marketing, Revenue Operations, Billing, Customer Experience, and IT to identify high-impact opportunities for AI-driven solutions that improve scalability and efficiency.

We are builders at heart. We value a strong sense of ownership, intellectual curiosity, and a bias toward action.

This is a hybrid role requiring 2-3 days per week on-site in Menlo Park with the team.

• →Build and deploy LLM-powered applications (retrieval systems, AI agents, workflow automation, vector storage) that integrate with internal systems and data sources
• →Partner with business stakeholders to identify automation opportunities, scope requirements, and define success metrics
• →Build lightweight data pipelines and analytics to support AI applications and measure their impact
• →Own projects end-to-end: from prototyping and iteration through production deployment and monitoring
• →Establish best practices for prompt engineering, evaluation, and responsible AI use as the team scales
• →Develop and lead internal training sessions on LLM fundamentals, prompt engineering, and AI-assisted development tools

• 5+ years of experience in software engineering, data science, or ML engineering
• Hands-on experience building applications with LLM APIs (OpenAI, Anthropic, etc.)
• Strong Python proficiency and comfort with SQL and relational databases
• Experience deploying and maintaining production systems
• Familiarity with AWS
• Excellent communication skills and ability to translate business problems into technical solutions
• Self-directed and comfortable with ambiguity in a 0-to-1 environment

• Previous entrepreneurial experience
• Experience with retrieval architectures, vector databases, and embedding models
• Familiarity with agent frameworks or workflow orchestration tools
• Experience with traditional ML frameworks (scikit-learn, PyTorch, TensorFlow)
• Prior work in healthcare, biotech, or other regulated industries

Unity Complete™ is the only non-invasive prenatal screen capable of assessing fetal risk for both common recessive conditions and aneuploidies from a single maternal blood sample. Our Northstar® liquid biopsy test uniquely combines treatment selection with real-time monitoring, giving oncologists unprecedented precision in cancer care.

From $0 to $150M+ in Annual Recurring Revenue in just five years. In 2025, we completed one of the most successful IPOs for a medical diagnostics company, building on nearly $400M in private funding,including our $130M Series D in 2024 and backed by world-class investors including Hummingbird, Adams Street Partners, Neuberger Berman, Baillie Gifford, and Premji Invest.

Forbes named us one of America's Best Startup Employers for 2025 and we're Great Place to Work certified, with 100% of our people willing to go the extra mile, even as we've scaled to over 700 employees.

Headquartered in Menlo Park with facilities in Union City, CA, and a new lab opening in Austin, TX in 2027, we're continuing to push the boundaries of what's possible in molecular diagnostics. We're just getting started.

Ready to help us change the world, one molecule at a time? Learn more at billiontoone.com