Senior Software Engineer, Digital Experience

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.

We are currently looking for a high-performing Senior Software Engineer, Digital Experience to join our dynamic software engineering team. Software engineers at BillionToOne work in highly collaborative and interdisciplinary teams of clinicians, computational biologists, and other engineers to robustly scale personalized genomic medicine to millions of patients. If you have experience performing in a full life-cycle development, love seeing your work positively affect your colleagues and patients, and thrive in a fast-paced entrepreneurial environment, this could be a great opportunity for you. In this role, you can have an impact both through many small tools and large product development. This role is a hybrid (onsite 2-3 days/week) position.

Projects you may work on include:

• Build a seamless digital experience so clinicians and patients across a diversity of care centers and socioeconomic status can have access to BillionToOne’s highly complex genetic testing

• Help digitize laborious and error-prone paper-based workflows at busy OBGYN clinics

• Enable better transfer of care through portable electronic medical records

• Infuse joyful experiences into pregnancy

Technologies we use include: Python, Django, Postgres, React, Typescript, AWS, Salesforce, and emerging AI-assisted coding environments (e.g., Cursor, GitHub Copilot, Claude Code)

Responsibilities:

• Build and maintain robust applications and systems using React, Typescript, Django, Postgres, and other libraries.

• Collaborate with product design and product management to deliver delightful experiences for patients and providers.

• Foster a knowledge sharing culture within the team, contributing to the growth and development of colleagues through mentorship and collaborative learning.

• Demonstrate a creative and out-of-the-box mindset, offering innovative solutions and approaches to complex technical challenges.

• Prioritize quality by writing comprehensive unit tests and ensuring adequate test coverage across all components and modules.

• Demonstrate a strong sense of ownership and take responsibility for end-to-end project delivery. The ideal candidate will thrive in an environment where they have the autonomy to make informed decisions and take the initiative to drive projects forward.

• Champion engineering excellence through architectural best practices, code quality standards, and thoughtful code reviews that emphasize both functionality and security.

• Apply a security and compliance mindset ensuring adherence to relevant regulations while implementing appropriate safeguards for sensitive patient information.

• Confidently challenge ideas and assumptions from stakeholders when necessary, while at the same time, leverage their expertise and insights to improve the overall solution.

Requirements:

• 5+ years of professional software development experience with a proven track record of delivering complex projects and adhering to best practices

• Deep experience with modern frontend technologies, specifically with Typescript, React, and CSS-in-JS libraries

• Have implemented frontend architecture best practices such as component systems, npm workspaces, Storybook, and Playwright testing

• Experience with web frameworks such as Django

• Familiarity with modern AI-driven development practices and tools.

• Excited about working in-person with our team in Menlo Park

Nice-to-haves:

• Previous startup or entrepreneurial experience

• Experience in driving products from zero to one

• Familiarity with healthcare data and standards like FHIR and HL7

• Interest in engaging with and applying LLMs

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)

• Free 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 $297,321 per year, including a base pay range of $190,081 - $211,201 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.

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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 www.billiontoone.com