About the Role 

Multisynaptech is looking for a Senior C# .NET Backend Developer to join our development team and help build a brand-new web-based platform from scratch. 

You’ll be one of the backend engineers, working closely with frontend and infra engineers. This is a unique opportunity to shape the product architecture, influence technology choices, and lay the foundation for a scalable, secure, and high-quality product that simplifies healthcare workflows and improves patient outcomes. 

If you're a hands-on developer with strong decision-making capabilities and a passion for clean, maintainable systems — let's talk. 

What You’ll Do 

Core Responsibilities 

• Design and develop a modern, scalable backend application using C# on .NET Core, serving microservices to a Vue.js frontend. 
• Build secure APIs and integrate databases (SQL and NoSQL). 
• Collaborate on key design and architecture decisions — your input is essential. 
• Ensure the system meets healthcare-grade security, performance, and scalability requirements, aligning with relevant certifications (ISO 27001, NEN 7510). 
• Contribute to CI/CD pipelines and DevOps practices in collaboration with platform engineers. 

Integration Responsibilities 

• Design and develop robust integrations with external systems such as EHR platforms, payment providers, and other healthcare APIs. 
• Develop data mapping and transformation logic to build integrations that can easily be swapped to prevent vendor lock-in. 
• Work with healthcare standards such as HL7 FHIR, DICOM, or other relevant protocols. 
• Support real-time data streams and ESB-like messaging systems. 

Who You Are 

• Open and approachable — we work hard, but we also have a lot of fun. 
• 5+ years of professional experience as a backend or full stack developer with a strong backend focus. 
• Proven track record of taking ownership of software products and technical architecture from the ground up. 
• Deep knowledge of C# and .NET Core. 
• Experience with cloud platforms (preferably Azure), containerization, and backend engineering in cloud-native environments. 
• Familiarity with ESB concepts and message queueing systems. 
• Strong communicator with a collaborative mindset. 
• Based in the Netherlands (Rotterdam area). 
• Comfortable working on-site full-time for the moment — we need to work closely together in order to build a great foundation fast. This will probably change over time. 

Nice to Have 

• Experience with SaaS platforms. 
• Experience with healthcare integrations (care systems, lab interfaces, etc.). 
• Interest or experience with Go or Rust. 
• Familiarity with authentication protocols such as SAML, OAuth 2.0. 
• Knowledge of security best practices and performance optimization. 
• Prior experience in agile and/or startup environments. 

What We Offer 

• A unique opportunity to build a new product from the ground up. 
• A flexible work culture with autonomy and trust. 
• A diverse, motivated and driven team that values collaboration, innovation, and ownership. 
• Competitive compensation with the option for performance-based bonuses or equity participation. 
• Long-term collaboration potential (freelance or permanent arrangements depending on fit). 

Interested? 

Send your CV to [email protected] 

Let’s discuss how you can help us build something impactful at Multisynaptech.