Senior AI Engineer I

Ready to redefine what's possible in molecular diagnostics?

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

• Working alongside brilliant, kind, passionate and dedicated colleagues, in an empowering environment, toward a global vision, striving for a future in which transformative molecular diagnostics can help millions of patients
• Open, transparent culture that includes weekly Town Hall meetings
• The ability to indirectly or directly change the lives of hundreds of thousands patients
• Multiple medical benefit options; employee premiums paid 100% of select plans, dependents covered up to 80%
• Extremely generous Family Bonding Leave for new parents (16 weeks, paid at 100%)
• Supplemental fertility benefits coverage
• Retirement savings program including a 4% Company match
• Increase paid time off with increased tenure
• Latest and greatest hardware (laptop, lab equipment, facilities)
• Daily on-site lunches provided from top eateries
• A variety of perks on campus (state of the art gym, restaurant)
• Free on-site EV charging (compatible with all EVs, including Tesla)

At BillionToOne, we are proud to offer a combination of a (1) base pay range (actual amount offered is based on experience and salary/equity options split that the candidate chooses), (2) generous equity options offering, (3) corporate bonus program, on top of (4) industry leading company benefits (free healthcare options, 401k match, very generous fully paid parental leave, etc.).

For this position, we offer a total compensation package of $280,705 per year, including a base pay range of $174,241 - $200,641 per year.

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BillionToOne is a next-generation molecular diagnostics company on a mission to make powerful, accurate diagnostic tests accessible to everyone. Our revolutionary QCT molecular counting technology enhances disease detection resolution by over a thousandfold using cell-free DNA,a breakthrough that has already transformed the lives of over half a million patients worldwide.

Our Impact

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.

Our Growth

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.