Mendix Developer – Legacy Application Modernisation

HumanInTech; Brussel Hoofdstad; Hybrid; EUR 45,000 - 80,000; Part time

Job summary

HumanInTech is seeking a Mendix Developer to join a multidisciplinary team modernising a legacy application in Brussels. You will contribute to AI-assisted development, build screens, microflows and integrations, and perform unit testing as part of a phased migration project.

The role requires 3–5 years of Mendix experience, relevant certifications or equivalent, and fluency in Dutch, English and French. The assignment runs for 25 months, hybrid in Brussels, with part-time to full-time

Qualifications

• Mendix Intermediate Advanced Developer certification or higher, or equivalent experience.
• Expert-level Mendix development skills.
• Experience with AI-assisted development.
• Experience with complex business processes.
• Experience with Agile/Scrum.
• Proficiency in Dutch, English and French.

Responsibilities

• Developing user stories
• Adapting and extending AI-generated components
• Building screens, microflows and integrations
• Performing unit testing

Skills

Mendix development

AI-assisted development

Agile/Scrum

Dutch language

English language

French language

Education

Bachelor's degree

Tools

Mendix Studio Pro

Job description

What you will do

You will join a multidisciplinary team modernising a legacy application with over 150,000 lines of code and around 20 modules. The application currently supports case management, data processing and reporting, and will be migrated to a future-proof low-code platform using modern techniques including AI-assisted development, code analysis and model-driven approaches.

Your responsibilities as Mendix Developer include:

• Developing user stories
• Adapting and extending AI-generated components
• Building screens, microflows and integrations
• Performing unit testing

The project is structured in three phases to spread investment across three budget years. Each phase delivers a standalone deliverable that can be used independently of future phases. Each phase is ordered separately.

What we are looking for

• Mendix Intermediate Advanced Developer certification or higher, or equivalent experience
• Expert-level Mendix development skills
• Confirmed experience with AI-assisted development
• Confirmed experience with complex business processes
• Confirmed experience with Agile/Scrum
• Active knowledge of Dutch, English and French

You must provide all requested certificates and documents with your CV so they can be validated.

The setting

This assignment runs for 25 months from December 2026 to the end of December 2028, part-time at 2/5. The work is hybrid, based in Brussels. The actual start and number of days depends on budget approval.

The team will use innovative and automated migration methodologies that leverage artificial intelligence, code analysis and model-driven development to ensure a faster, high-quality and controllable migration. The proposed solution must have been successfully applied in a completed or ongoing project.

You can join us for this assignment as a freelancer or as an employee of HumanInTech. Same role, same team. If you join as an employee, your employment continues beyond this assignment. When it ends, we’ll work together to find your next assignment.

Location: Brussels, hybrid

Work address: Belgium

Employer / contracting party: HumanInTech

Applications close (Brussels time): October 21, 2026 at 2:00 AM

Engagement: Freelance or employed by HumanInTech

Working hours: Full-time

Experience: 3–5 years or more

Education: Bachelor's or more

Published: October 2026