Principal Software Engineer - TypeScript/Python in England

The Challenge

Healthcare technology requires seamless integration of patient-facing applications, clinical systems, external partners, and financial workflows—while maintaining the security, reliability, and auditability that regulated environments demand. As healthcare AI advances and new treatment models emerge, the industry needs engineering leaders who can architect scalable platforms, drive technical excellence, and deliver production-grade systems that translate clinical requirements into real-world outcomes.

Own the technical delivery and architecture of Onsera's core product platforms, from wearables integration and health data pipelines to member payments and AI workflows. As a player-coach, you'll design and implement full-stack solutions while setting engineering standards and help build and mentor our engineering team as we scale. This role offers the opportunity to shape API-first architectures, lead complex integrations with healthcare partners and SaaS platforms, and transition into engineering leadership as the organization scales.

• Design and implement full-stack solutions spanning frontend applications, backend services, APIs, agentic systems and third-party integrations.
• Architect and implement member payment platforms, including fee collection, reconciliation, and financial reporting.
• Define and enforce software engineering standards, including coding conventions, testing practices, and documentation.
• Conduct rigorous code reviews focused on correctness, security, performance, and maintainability.
• Mentor engineers and gradually transition into line management as the engineering organization grows.

8+ years of experience as a Full-Stack Engineer delivering production systems, with track record at Senior or Principal level.

• Proficiency across frontend and backend development, including modern web frameworks and API design.
• Strong background in automated testing strategies and quality-driven development.
• Experience acting as a technical leader or player-coach with demonstrated ability to mentor engineers.
• Comfortable collaborating with product, data, clinical, and non-technical stakeholders.
• Experience working with Python.
• Experience with payments, billing, or financial reconciliation systems.
• Experience in healthtech, regulated environments, or sensitive data systems.
• Familiarity with health data ingestion, wearable platforms (Apple HealthKit, Google Fit, Fitbit), or healthcare interoperability patterns.
• Exposure to FHIR-based data exchange or healthcare integration standards.
• Prior involvement in scaling engineering teams or platforms during growth phases.

Ground-floor opportunity to shape technical architecture and engineering culture.

• Direct collaboration with product managers, data scientists, ML engineers, and clinical experts.
• Growth path into engineering leadership as the organization scales.
• Competitive salary and benefits package, including participation in our equity program.

We are an early-stage health AI company revolutionizing cardiometabolic care and population health economics. Our unique position within the PHP ecosystem provides:

• A proven track record of success in building biotech and healthcare companies.
• Funding and resourcing to support deep tech and scientific R&D—and to drive growth.
• Direct access to industry pioneers (including founders of The Medicines Company and Metsera), strategists (McKinsey/QuantumBlack alumni), and world-class scientific talent (e.g., scientific leaders at Oxford University, Ellison Institute of Technology).

Expert network: About PHP

Population Health Partners (PHP) is a premier investment firm established in 2020, aimed at transforming health outcomes for large populations. With offices in New York and London, PHP combines financial resources with industry-leading capabilities and technology.