Senior Software Engineer, Prenatal

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 the 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 prenatal 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 working across the full development lifecycle, 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 3 days/week) position.

Projects you may work on include

• Scaling and future-proofing core systems to support rapid volume growth, enterprise workloads, and long-term platform expansion.
• Building shared platform libraries and modular, domain-aligned services that reduce coupling, improve maintainability, and enable teams to integrate and deliver independently.
• Driving core architectural initiatives including service boundaries, data flows, observability patterns, and modernization of legacy components to enhance reliability and developer velocity.
• Establishing foundational infrastructure and automation that strengthens deployment workflows, improves system health visibility, and enables consistent, high-quality engineering execution.

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

Responsibilities

• Design, build, and operate scalable, high availability backend services, APIs, and data integrations that power customer facing product experiences
• Lead technical delivery across the full lifecycle: architecture, design, implementation, testing, deployment, and ongoing operations
• Collaborate closely with product, design, and cross functional engineering teams to deliver performant, reliable, and intuitive platform capabilities
• Develop clean abstractions and platform APIs that simplify complex LIS workflows while balancing developer velocity with long term system stability
• Build and maintain secure, reliable cloud infrastructure on AWS, including compute environments, networking, container orchestration, storage, and environment automation
• Implement CI/CD pipelines, Infrastructure as Code, configuration management, and automated environment provisioning to standardize and accelerate delivery
• Embed observability and operational excellence into the platform by default through robust monitoring, logging, alerting, and reliability patterns
• Ensure the scalability, maintainability, and overall health of backend and cloud systems as the platform grows to support large enterprise workloads and future global expansion
• Foster a culture of ownership, technical excellence, lear