Senior Freelance Engineer (Mobile + Backend)

We’re looking for a Senior Freelance Engineer (Mobile + Backend) to partner directly with the founder in building a scalable, data-driven system in the Digital Health / Femtech space. This is a long-term, strategic collaboration with real influence on architecture, product direction, and system design with the potential for equity participation. Tasks Analyze and evolve existing systems into a clean, scalable architecture Own system design across mobile and backend, including data models and core logic Ensure robust integration between mobile and backend systems Lay the technical foundation for future features, algorithms, and product growth, and the evolution of business logic Communicate decisions clearly and transfer knowledge to founder to enable long-term system ownership Requirements Seniority: 5–8+ years of experience in real product environments with strong engineering standards (testing, code quality, production readiness) Strong experience with React Native, TypeScript , and mobile architecture Advanced backend expertise ( AWS ) Proven experience designing scalable architectures and refactoring complex systems, including modeling complex, state-driven systems and data logic Experience with data modeling, system design, and data-driven or algorithmic products Solid understanding of GDPR and handling sensitive data Interest in (female) health and hormonal systems Experience in digital health startups Benefits Flexible, remote-first work Personal coaching support Meaningful work: direct impact on women’s health through product and system design Fair, structured compensation and a long-term perspective for strong collaboration How You’ll Work: Freelance setup (individual or max. 2 people) 10–20 hours/week, working directly with the founder with a collaborative style that includes independent ownership, pair programming, code reviews, and architecture discussions. Please send: Relevant projects (especially refactoring and system design/building) A brief description of your approach to working with complex codebases GitHub, code samples, or other insights into how you work Find Jobs in Germany on Arbeitnow