Senior Frontend Engineer

Medis Medical Imaging is driven by a bold ambition: to transform complex cardiovascular imaging into intuitive software that enables medical professionals to work smarter, faster, and with greater confidence. For over 30 years, Medis has pioneered advanced imaging tools, making them accessible to researchers and clinicians worldwide. Today, we build on this legacy with a forward-looking roadmap powered by AI innovation.

Working at Medis is both purposeful and inspiring. You'll be part of a fast-paced, innovation-led company with a global presence, rooted in a strong heritage and a pioneering spirit. Our culture is built by smart, hands-on people who take ownership and care deeply about their work and each other. We value connection, curiosity, and collaboration. We take pride in delivering technology that truly makes a difference.

We are looking for a Senior Frontend Engineer who is a true expert in React and modern frontend development. This is not a role where you will learn React on the job – we need someone who has already mastered it and can bring that expertise from day one.

You will own the frontend architecture of a sophisticated medical imaging application, write high-quality production code, and serve as the go-to technical authority for React and TypeScript within the team. A core part of your responsibility will be mentoring and guiding less experienced team members, raising the bar for frontend practices across the engineering organisation.

While this is a frontend-focused role, we are looking for someone with a genuine interest in backend development and a full-stack mindset. Our applications are built on C#/.NET and use gRPC for communication, and we value engineers who are curious about the entire system, not just the browser.

This is a high-impact position where your code will be used in clinical environments, requiring both technical excellence and attention to quality standards in regulated medical software.

• Lead frontend development – design, build, and maintain a modern React application for medical image analysis, making key technical decisions on patterns, tooling, and code organisation.
• Mentor the team – guide and coach less experienced engineers in React best practices, code review, component design, and frontend architecture. You set the standard others follow.
• Build complex visualisations – implement medical imaging features using Cornerstone.js and VTK.js for 2D and 3D DICOM rendering, annotation tools, and multi-viewport support.
• Deliver high-performance UIs – create responsive, performant interfaces for real-time clinical workflows using React 19, MobX, and Material UI.
• Integrate with backend services – work with gRPC and Protocol Buffers to connect the frontend to our .NET backend and collaborate closely with backend engineers.
• Champion code quality – enforce TypeScript strict mode, maintain comprehensive ESLint rules, and establish testing strategies to ensure reliability in clinical software.
• Support internationalisation – maintain and extend our multi-language support across 6+ languages for global deployment.
• Contribute beyond the frontend — as your interest and the team's needs align, take on backend tasks in C#/.NET and grow into a broader full-stack role over time.

• 5+ years of professional frontend development experience with a strong focus on React.
• Expert-level React knowledge – hooks, context, performance optimisation, component architecture, and modern React patterns. You should be the person others come to for answers.
• Strong TypeScript proficiency with strict typing practices and a deep understanding of the type system.
• Proven experience with state management libraries (MobX, Redux, Zustand, or similar) in complex production applications.
• Mastery of modern build tooling (Vite, Webpack, or similar) and understanding of bundling, code splitting, and performance tuning.
• Experience with component libraries such as Material UI, and skill in building consistent, accessible, design-system-driven UIs.
• Track record of mentoring or leading – you have helped other engineers grow through code reviews, pair programming, architectural guidance, or knowledge-sharing.
• API integration experience with RESTful APIs; familiarity with gRPC / Protocol Buffers is a strong plus.
• Strong debugging and performance optimisation skills – you can profile, diagnose, and fix complex frontend issues independently.
• Excellent English communication skills, both written and spoken.

• Experience with medical imaging software, DICOM standards, or healthcare/medical device development.
• Knowledge of Cornerstone.js, VTK.js, or similar medical visualisation libraries.
• Familiarity with FDA/CE regulatory requirements for medical software (ISO 13485, IEC 62304).
• Backend experience with C# / .NET – even at a junior level – showing genuine full-stack interest.
• Experience with end-to-end testing frameworks (Playwright, Cypress).
• Understanding of OIDC / OAuth2 authentication flows.

• A rewarding and competitive compensation package, with both fixed and variable components.
• A pension plan with strong employer contribution.
• Flexibility to purchase additional leave days.
• A diverse, collaborative, and international team culture with colleagues across Europe, the US, and Asia.
• The chance to work on innovative solutions that truly impact patient care and the future of cardiovascular healthcare.
• A hybrid work model – 2 days per week in our Leiden office, with flexibility for the rest.