Senior Software Engineer (Team Contract)

Build the technology behind our holiday contracts At Sunweb Group, we are developing a new internal application for creating and managing contracts with our suppliers and contractors. As our Senior Software Engineer, you will help build this application from the ground up and replace an existing legacy solution with a modern, future-ready platform. You will have the opportunity to shape both the technical foundation and the way the new team works. This is a new team with an initial size of approximately two to three engineers. You will first be onboarded within Team Dalyan, working in a group of around five colleagues. Once the new Contracting Team is established, it will separate into its own team with a dedicated scope and responsibilities. Location: Rotterdam Sunweb Group office (Hybrid) Start date: December 2026 Availability : Fulltime What you’ll do • Design and build a new application for creating and maintaining supplier contracts. • Develop cloud-native solutions using C#, .NET and Microsoft Azure. • Build user-friendly React applications for internal users. • Help replace a legacy application with a scalable and maintainable modern solution. • Contribute to system design, architecture and data-modelling decisions. • Develop reliable integrations and work with SQL-based data. • Apply automated testing, CI/CD and DevOps practices throughout the development lifecycle. • Communicate technical decisions, progress, risks and dependencies clearly. • Take ownership from initial design through delivery and production. • Collaborate with contractors, suppliers and internal teams that depend on accurate contracting information. • Use GitHub Copilot and other supporting tools to improve productivity and software quality. Our tech stack C# · .NET · Microsoft Azure · SQL · React · GitHub · GitHub Copilot · CI/CD · Automated Testing · DevOps What you bring • At least five years of professional experience with C# and .NET. • Experience building cloud-native applications on Microsoft Azure. • Strong SQL and data-modelling skills. • Solid system-design experience. • The ability to apply clean-architecture principles pragmatically. • Experience developing React applications, preferably for internal tools. • Experience with CI/CD, automated testing and DevOps practices. • Experience modernising or replacing legacy systems. • Clear communication skills and the ability to make progress, risks and dependencies visible. • An ownership mindset: you follow work through from idea to delivery. • A pragmatic approach that balances engineering quality with delivery needs. • Strong stakeholder communication skills in English (Dutch is a big plus). What we offer • Yearly gross salary between 65K and 80K, excluding 8% holiday allowance). • 25 holidays + 6 ATV days, based on fulltime employment. Please note: ATV days do not apply to part-time contracts. • Enjoy up to 20% off when booking with our brands for you, your family, and your friends. • As an international company we support a hybrid way of working. We provide you with office furniture and IT equipment. • A personalized Reflect & Develop Plan to support your career growth. • Benefit from coaching sessions designed to support your well-being. • Receive work-from-home and travel allowances to ease your daily routine. About Sunweb Group Sunweb Group is one of Europe’s largest online travel platforms, with over 1.3 million customers annually. We operate in 8 international markets with 500+ colleagues across Europe. We combine scale with a fast-moving, ownership-driven culture where teams are trusted to build and improve continuously. Why this role is interesting • Build a new application instead of only maintaining an existing system. • Influence technical decis