Senior .NET Developer - Team Rewriting/Migration to .NET 10

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Senior .NET Developer - Team Rewriting/Migration to .NET 10 (Freelance) - 4 months - Brussels Belgium

Intro

Are you ready to architect the future of business-critical systems? RELYzIT Talent is seeking a Senior .NET Developer to join a high-impact migration project for our client, modernizing essential information tools that power their Benefits Service. This is a freelance opportunity for elite builders who thrive on challenge, innovation, and lasting impact.

Why This Role Matters

Our client is embarking on a strategic migration to modernize and future-proof the backbone of their Benefits Service. As a Senior .NET Developer, you will be instrumental in rewriting and elevating core business applications to .NET 10, ensuring service continuity, scalability, and technical excellence. Your expertise will directly influence the reliability and performance of systems that thousands depend on daily.

What You’ll Be Doing

• Designing, developing, and maintaining robust software solutions using Microsoft technologies, with a focus on .NET (Framework and Core).


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


• Providing technical mentorship and fostering a culture of excellence within the development team.


• Conducting code reviews and ensuring adherence to best practices and coding standards.


• Translating functional requirements into effective technical solutions in close partnership with analysts.


• Ensuring the quality, performance, security, and maintainability of all applications delivered.


• Optimizing system performance and proactively identifying areas for improvement.


• Integrating and evaluating new technologies aligned with evolving business objectives.

What We’re Looking For

• Proven expertise in building and maintaining complex .NET solutions, with a strong focus on sustainability and performance.


• Ownership mindset: you take initiative, drive outcomes, and deliver with pride.


• Critical analysis and structured, solution-oriented thinking.


• Ability to generate viable alternatives and draw relevant, actionable conclusions.


• Technical leadership and a collaborative, mentoring spirit.


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

Technical Skills

• ASP .NET Web API (Expert)


• C# / .NET (Core, 10) (Expert)


• Entity Framework Core (Expert)


• Authentication/Authorization (JWT, OIDC, claims) (Confirmed)


• Blazor (Confirmed)


• MVC (Confirmed)


• REST, Swagger/OpenAPI (Confirmed)


• SQL Server (Confirmed)


• Testing (unit + integration) (Confirmed)

Language Proficiency

• Mastery of either French or Dutch at CEFR level C2


• Very good command of English at CEFR level C1

Other Requirements

• Experience in technical mentoring and code review


• Strong analytical and information integration skills


• Ability to work partially remote, with presence in Brussels as required


• Experience in migration or rewriting projects is a plus

About the Role

• This is a freelance position for a duration of 4 months, based in Brussels, Belgium.


• Join a team of elite builders, vetted through RELYzIT Talent’s VECTOR7™ Signal Stack, and make a tangible impact on mission-critical systems.


• Be part of a builder-first community where your expertise is recognized, valued, and amplified.