Senior Application Developer (Freelance) – Brussels

About the role

Our client is looking for a Senior Application Developer on a six‑month freelance mission in Brussels. You will be responsible for keeping critical legacy applications stable, secure, and ready for future modernization. The role combines hands‑on technical work with close collaboration with functional analysts and other technical experts.

Key responsibilities

• Lead corrective, evolutionary, and continuous improvement of PowerBuilder, ASP.NET and SQL‑based applications.
• Provide production support, incident resolution and small‑scale development or functional adaptations.
• Work with functional analysts to ensure technical solutions match business needs.
• Perform technical analysis, identify risks and optimise application performance.
• Drive technical evolutions required for the progressive modernization of legacy systems.
• Ensure all work follows the i‑CITY methodology, standards and best practices.
• Work on‑site in Brussels at least two days per week (hybrid model).

Required profile

• Proven experience managing and evolving legacy applications, especially PowerBuilder and .NET.
• Builder mindset with ownership, initiative and a passion for solving complex technical challenges.
• Strong analytical skills for risk identification and performance optimisation.
• Effective collaboration and clear communication with cross‑functional teams.
• Commitment to best practices, quality and continuous improvement.
• Experience with defined methodologies such as i‑CITY or similar frameworks.
• Availability for hybrid work in Brussels (minimum two days onsite per week).
• Professional proficiency in English; elementary Dutch and French are a plus.

Required skills

• .NET (expert level)
• Architecture Distribution Service (expert level)
• PL/SQL (expert level)
• PowerBuilder (expert level)
• SAP SQLCA (expert level)
• Windows Services (expert level)
• ASP
• SQL