Senior Full Stack Engineer (Core Platform & API Squad)

Do you want to build the platform at the core of a health-tech operation that touches hundreds of thousands of lives? Tell us what you need to make it happen. The more successful we are, the more people we help lead healthier, happier lives.

About Wellis

Wellis is a healthtech scale-up reinventing one of the most traditional sectors there is: healthcare. We started three years ago. Today we serve tens of thousands of customers, and we're only getting started. We combine medical expertise with technology and data to make care accessible, personal, and seamless. People use our platform to take control of their health journey with trusted medical support and tailored programs. We move fast and challenge conventions, because better healthcare should be within everyone's reach.

The Role

You'll be a core member of the Core Platform & API squad, building the engine behind everything Wellis does. Our API layer is in its early days and needs rethinking and scaling for where the platform is headed, so the work is close to greenfield. You'll shape the data model, the internal API serving our web portal and mobile app, and the business logic behind prescription and medication workflows. The stakes are real. The data is patient medication records, and the people consuming your APIs are pharmacists making clinical decisions.

Our stack is TypeScript end to end: React on web, React Native on mobile, Node on the backend. One language and one type system across all of it, so a prescription gets defined once and the compiler enforces it from database to screen. You'll be the backend anchor of that stack. That means bringing real systems discipline: transactions, idempotency, migrations, queues.

We're an AI-native engineering team. Agentic coding tools are our primary way of working, and we expect you to work this way from day one. We also expect you to make our agents better. The skills, plugins, and workflows you write should raise the output of everyone around you.

What You'll Build

• The core API layer. What exists today is early-stage, so you get to redesign it properly. Build the internal Node/TypeScript API serving web and mobile: schema-first design, runtime validation at every boundary, auth, pagination, versioning. These are the contracts every other squad will depend on.
• The data layer. Own the schema covering patient management, clinical data, prescriptions, providers, and devices. Migrations, indexing, query performance, data integrity, across SQL and NoSQL stores as the platform demands.
• Business logic. Prescription workflows (create, validate, dispense, track), medication record management, patient lifecycle, clinical rules, drug interaction checks.
• Agentic tooling. Build and maintain the skills, plugins, and agent workflows the team develops with. This is the leverage layer that lets a small team ship like a big one.
• Integration touchpoints. Data flows with billing, logistics, and ERP systems, plus an external Dutch pharmacy information system.

What we offer

• Salary range € 7.000 - € 10.000 gross per month (depending on experience)
• Pension plan
• Learning budget
• Monthly personal budget (Alleo)
• Hybrid working: partly from our new office in central Rotterdam (2 days)
• 20 days of remote working per year
• Working from home allowance (2 days a week)
• A culture of short lines, speed, and continuous improvement — where pragmatism and impact matter.
• The opportunity to help build a fast-growing healthtech scale-up from the inside.