Senior AI Engineer

Ready to redefine what's possible in molecular diagnostics?

Join a team of brilliant, passionate innovators who wake up every day determined to transform healthcare. At BillionToOne, we've built something extraordinary—a culture where transparency fuels trust, collaboration drives breakthroughs, and every voice matters in our mission to make life-changing diagnostics accessible to all. We don't just aim for incremental improvements; we strive to build products that are 10x better than anything that exists today. Our people are our greatest asset: talented scientists, engineers, sales professionals, and visionaries 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—every innovation you contribute helps remove fear of unknown from some of life's most critical medical moments. If you're driven by purpose, energized by innovation, and ready to help build the future of precision medicine, 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 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.

Responsibilities:

• 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

Qualifications:

• 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

Nice-To-Haves:

• 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

Benefits And Perks:

• 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.

BillionToOne is an equal opportunity employer. We do not discriminate on the basis of race, religion, color, national origin, gender, sexual orientation, age, marital status, veteran status, or disability status.

For more information about how we protect your information, we encourage you to review our .

About BillionToOne

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's already transformed the lives of over half a million patients worldwide.

Our Impact: We've pioneered game-changing diagnostic solutions that are redefining industry standards. Unity Complete™ stands as the only non-invasive prenatal screen capable of assessing fetal risk for both common recessive conditions and aneuploidies from a single maternal blood sample. In oncology, 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 $125 million in Annual Recurring Revenue in just four years. We've raised close to $400 million in funding, including a $130 million Series D round in June 2024, achieving a valuation of over $1 billion. This backing comes from world-class investors including Hummingbird, Adams Street Partners, Neuberger Berman, Baillie Gifford, and Premji Invest.

Our Recognition: Forbes recently named us one of America's Best Startup Employers for 2025 , and we were awarded Great Place to Work certification in 2024—with an incredible 100% of our people reporting they are willing to give extra to get the job done . These honors recognize not just our innovation but the exceptional culture we've cultivated—one that remains authentically collaborative and transparent even as we've scaled.

Our Future: Headquartered in Menlo Park with facilities in Union City, California, we're continuing to push the boundaries of what's possible in molecular diagnostics. Recent clinical outcomes data for Unity Fetal Risk Screen and new advances in cancer diagnostics prove we're just getting started.

At BillionToOne, you'll join a diverse team of passionate innovators who believe that the best science happens when brilliant minds collaborate openly, think boldly, and never lose sight of the patients whose lives depend on our work.

Ready to help us change the world, one diagnosis at a time?

Learn more at