Senior Software Engineer, Oncology

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 to join our dynamic software engineering Oncology 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 Oncology clinics
• Enable better transfer of care through portable electronic medical records

Technologies We Use

Python, Django, Flask, Postgres, AWS, Alpine.js, HTMX, Salesforce, and emerging AI-assisted coding environments (e.g., Cursor, GitHub Copilot, OpenAI).

Responsibilities

Collaborate with talented engineers to design and develop our services, data processing pipelines, and interfaces, driving innovation and efficiency

Build user-facing features to optimize performance and reliability, enhancing overall user experience

Elevate BTO Oncology’s backend systems, including the test order record database, third-party integrations, test scheduling and reports management software, and distributed systems architecture, to ensure they meet the highest standards

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

Prioritize quality by writing comprehensive unit / integration / end-to-end tests and ensuring superior test coverage across all components and modules. Highly skilled in writing technical documentation and validation reports that assure correct functionality of medical informatics systems

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

Collaborate cross-functionally, actively seeking input from team members and fostering a positive and inclusive work environment

Qualifications

• 5+ years of professional software development experience with a proven track record of delivering complex projects and adhering to best practices
• Expertise in Python backend frameworks (e.g., Django or Flask), delivering high-quality, scalable code
• Strong foundation in cloud services, preferably AWS, including ECS, S3, AWS Batch, EC2,