Technical Co-Founder (Full-Stack Developer)

ROLE DESCRIPTION

This is a technical co-founder opportunity at Calibre Social — a Copenhagen-based hybrid role, part-time to start with a clear path to full-time as the company grows. Calibre is a social platform that helps people build real friendships around shared passions and turns those connections into in-person experiences with local businesses. The Full Stack Engineer (Technical Co-Founder) will own the design and development of Calibre’s backend from the ground up and contribute to the React Native mobile frontend. Responsibilities include architecting the data model and API layer, implementing authentication and core app logic, collaborating directly with the founder on product decisions, writing clean and testable code, and supporting deployment and monitoring in production. Product design and UI are covered by the founding team (Figma/Adobe XD), so the focus is on architecture and engineering, not visual design. Compensation is equity-based (substantial founding stake, open to negotiation), with a cash component planned as part of the upcoming pre-seed raise.

QUALIFICATIONS

• Strong proficiency in full-stack development, with experience building and shipping modern mobile or web applications.
• Demonstrated back-end skills: server-side development, API design, relational databases (PostgreSQL preferred; we’re building on Supabase), and auth flows.
• Experience with React Native and/or React; comfort with JavaScript and the Expo ecosystem is a strong plus.
• Strong knowledge of modern web technologies and frameworks (e.g., JavaScript/TypeScript, React or similar, Node.js or equivalent server-side stack).
• Familiarity with version control (Git), testing (e.g., Jest), and modern deployment workflows (e.g., EAS Build, CI/CD).
• Understanding of app security, performance optimization, and cloud-based infrastructure.
• Comfort with early-stage ambiguity — architecting fresh rather than executing a spec, and helping shape technical direction.
• Ability to work in a hybrid setup in Copenhagen and communicate clearly in English.
• Bachelor’s in Computer Science or equivalent practical experience; startup experience and interest in social/community-focused technology are a plus.

Loneliness is one of the biggest under-addressed public health issues (SDG3) of our generation, and I think there’s a genuinely different way to build a social platform that treats it seriously. We’ve done the work to prove it: validated business case, an MVP-stage prototype, and a roadmap that’s grounded rather than hype-driven (MVP → Nordic growth → a Web3 layer, sequenced deliberately, not because it’s trendy). What’s missing is a technical co-founder to build it with — not for it.