Senior Outsystems developer

Feelance Developer OUTSYSTEMS

Brussels, Hybrid-3-month renewable contract

Mission

As a Senior OutSystems Developer, you play a key role in the design, development, and evolution of applications built on the OutSystems platform. You are involved throughout the entire application lifecycle, from technical analysis to production deployment and ongoing maintenance.

You are able to understand complex functional and technical analyses (UML, BPMN, data models), propose robust and scalable technical solutions, and ensure the overall quality of applications (performance, security, maintainability).

As a senior profile, you act as a technical reference within the team: you share OutSystems best practices, support junior developers, contribute to architectural decisions, and actively participate in the continuous improvement of development processes and standards:

• Design, develop, and maintain applications using Outsystems
• Participate in the analysis of functional and technical requirements
• Design, develop, and maintain applications using Outsystems
• Participate in the analysis of functional and technical requirements
• Propose appropriate technical solutions (architecture, performance, security)
• Develop APIs , web applications, desktop applications, or backend services
• Follow best development practices (SOLID principles, clean code, design patterns)
• Build and maintain a robust and scalable architecture
• Write testable, maintainable, and well-documented code
• Implement unit and integration test
• Solving issues
• Troubleshoot and fix bugs and production issues
• Refactor and improve existing applications
• Perform application monitoring and performance tuning
• Manage application lifecycle across environments (dev, test, prod)

Profile:

• 5+ years’ experience in application development, with the OutSystems platform.
• OutSystems platform (Service Studio, LifeTime, architecture, performance tuning, security).
• excellent knowledge of relational databases (SQL Server or equivalent).
• solid experience with integrations (REST/SOAP, APIs, third‑party systems).
• comfortable with both Frontend development (Reactive Web Apps, UX/UI) and Backend development.
• Experience with complex environments, application redesign, or migrations is an asset.
• You apply Agile/Scrum principles and actively contribute to team rituals.
• You pay close attention to code quality, testing, versioning, and deployment processes.
• French and/Or Dutch fluent (C2) + good English (B2)