Full-Stack Mobile Engineer [Product Engineer] (w/m/d)

ABOUT aGYM

People deserve more from the promise they make to themselves. More follow-through. More belonging. More of the person they actually came here to become.

The fitness industry isn't built to give them that. It makes its money when members fail, when they sign up in January full of resolve and never come back. aGYM is built the other way around: no contracts, no sign-up fees, cancel any time. We only win when people keep going. That single inversion changes everything we build.

Because once keeping people going is the whole game, you have to understand why people actually quit and the answer was never willpower. It's a 200,000-year-old brain wired to save energy, colliding with a busy life. That's why we've built a "phygital" product where physical and digital are inseparable. Every line of code exists to help people keep going.

Since opening our first gym in Berlin, thousands of members have already joined us. It's thousands today and soon to be millions.

We're a young, founder-led company. From the outside we might look like a gym with a nicer app. That's the surface. What we're really building is much bigger than fitness.

We're looking for people who love building products that change behaviour, who care deeply about engineering craft, and who can't stop asking why people do what they do.

ABOUT THE ROLE

Engineering is where aGYM's thesis becomes reality. Every system you build is two things at once. There's a craft layer that's fast, reliable and quietly invisible. The door opens instantly. Check-in never fails. The app doesn't make people wait. And there's a behavioural layer: every technical decision should help someone come back tomorrow.

As a Full-Stack Mobile Engineer, you'll own features from loosely defined problems all the way to production. You'll build the member app, the backend that powers our gyms and the internal tools that help the whole company operate more effectively.

You'll work directly with our founders in a small engineering team where ownership is expected, ideas are challenged and great engineering has a visible impact from day one. At aGYM, you won't be measured by tickets closed but by behaviour.

WHAT YOU’LL BE DOING

• Own features end-to-end, from discovery to production.
• Build and improve our Flutter mobile app, Next.js web applications and TypeScript Firebase backend.
• Build the software that powers the physical gym from access control and check-in to the operational systems members rely on every day.
• Turn behavioural hypotheses into product features and measure whether they actually change user behaviour.
• Own outcomes, not just output. Use product metrics to continuously improve what you build.
• Design systems that are reliable, scalable and built to grow from thousands of members to millions.
• Build internal tools that automate workflows and help the organisation move faster.
• Collaborate closely with product and design, contributing not just code but ideas.
• Present and defend technical decisions while staying open to better solutions.

WHAT MAKES YOU STAND OUT

• 3+ years building and shipping digital products across mobile and backend.
• Strong engineering skills in a typed language and a modern mobile framework. We use Flutter and TypeScript today, but we're more interested in your ability to learn than checking every box.
• Experience building and operating cloud-based applications (GCP or similar serverless platforms).
• Curiosity about AI-assisted software development and a willingness to continuously improve how you build software.
• Strong architectural thinking. You know when to optimise for simplicity and when to design for scale.
• Product sense and genuine curiosity about human behaviour.
• High ownership. You're comfortable taking ambiguous problems and driving them through to production.
• A reliability mindset. You understand that bugs don't just affect software, they affect real pe