Senior Developer .NET

Senior Developer .NET - Brussels, Belgium

At RELYzIT, we don't recruit — we build.

We unite exceptional builders: engineers, architects, creators, across the BENELUX and the GCC. Vetted through VECTOR7™'s multi-signal evaluation, you evaluate once and carry that credential forever. This is more than work. This is where builders build the future.

About the Role

RELYzIT Talent is seeking a Senior Developer .NET for our client in Brussels. This is a freelance opportunity for elite builders who want to shape robust, scalable software solutions using Microsoft technologies. You’ll be at the heart of impactful digital transformation, mentoring peers and driving technical excellence. Your work will directly influence the sustainability, performance, and security of mission-critical applications.

Why This Role Matters

As a Senior Developer .NET, you are not just writing code—you are architecting the backbone of digital services that empower organizations and communities. Your expertise will solve complex business challenges, ensure seamless user experiences, and future-proof essential systems. The stakes are high: your contributions will drive innovation, elevate technical standards, and inspire a culture of continuous improvement.

Key Responsibilities

• Design, develop, and maintain software components using .NET Framework and .NET Core.


• Collaborate with the architecture team to create scalable, future-ready technical solutions.


• Mentor and guide team members, fostering a culture of technical excellence and collaboration.


• Conduct thorough code reviews, ensuring adherence to best practices and high-quality standards.


• Analyze functional requirements with business analysts and translate them into robust technical solutions.


• Champion application quality, performance, security, and maintainability throughout the development lifecycle.


• Optimize system performance and proactively address bottlenecks.


• Integrate and evaluate emerging technologies aligned with business objectives.

Technical Skills

• ASP.NET Web API (proven expertise)


• Authentication/Authorization (JWT, OIDC, claims-based security)


• Blazor (junior level)


• C# / .NET (Core, version 10)


• Entity Framework Core


• MVC architecture


• REST APIs, Swagger/OpenAPI


• SQL Server


• Testing (unit and integration)

What We’re Looking For

• Proven experience as a full-stack .NET developer, with a strong track record of delivering impactful solutions.


• Critical thinker with the ability to analyze, synthesize, and integrate complex information.


• Structured, solution-oriented mindset with a passion for generating viable alternatives and drawing actionable conclusions.


• Technical leadership and a collaborative spirit—able to inspire, mentor, and elevate those around you.


• Resilience and adaptability in the face of technical and contextual change.


• Ownership mentality: you take responsibility for outcomes, not just tasks.

Language Proficiency

• Fluency in either French or Dutch (CEFR level C2)


• Very good command of English (CEFR level C1)

Other Requirements & Benefits

• Freelance position based in Brussels, with partial remote work flexibility.


• Engage in impactful ICT and Data projects that make a difference in society.


• Flexible working hours within a 40-hour workweek (core hours: 9:00–12:00 and 13:00–16:00).


• Modern, activity-based workspaces and easy access via public transportation.


• On-site amenities: parking, bike storage, individual lockers, and a company restaurant.


• Continuous self-development opportunities through our e-academy and Microsoft Enterprise Skills Initiative.

About RELYzIT Talent & VECTOR7™

RELYzIT Talent is not a recruiter-first platform—we are a builder-first community. Our VECTOR7™ Signal Stack ensures that every talent is rigorously vetted, so you evaluate once and carry that credential for life. We place elite tech professionals in roles that drive real impact and innovation, fostering a network where builders thrive and shape the future together.