Senior Mendix Developer

Bussum, hybrid | Full-time | €5,000 to €6,500 gross per month, plus 8% holiday allowance.

At PSOhub, you work on one product: a professional services platform used by companies around the world. Your work has two sides. You build new features and keep the platform fast, stable, and secure as we grow. And you build our MCP server, which lets Claude, ChatGPT, Gemini, and Copilot work with real operational and financial project data in PSOhub.

What you will work on

About 70% of your week is building. In our Mendix 11 app, you develop new features and keep improving performance, stability, and security. Alongside that, you develop the MCP server, connect it to the big LLMs, and build tools that let users take specific actions in PSOhub through AI. The other 30% is second-line support. When our Customer Success team can’t resolve an issue, you find the cause, fix it properly, and keep support posted. You see how customers really use what you build, and that makes you better at building it.

Who you will work with 

You will work directly with our CTO, exchanging ideas and leveraging each other’s experience. On a weekly level you will also work with Martijn van der Hoeden, our CEO and product owner. He has been building project management and PSA software for over 30 years. You discuss your ideas with the team that decides.

What you will work on

Mostly from home. Once a week we get together at our office, an estate in Bussum.

What you bring

• 4+ years of hands-on experience with Mendix, ideally working on commercial or customer-facing products.  
• Proven ability to work with and extend existing Mendix apps in a structured, thoughtful way.  
• Strong analytical thinking and problem-solving skills.  
• A proactive, hands-on mentality with the ability to lead by example.  
• Comfortable working directly with customer support and end users to investigate and solve issues. 
• A pragmatic mindset and the ability to balance long-term quality with short-term goals. 
• Solid knowledge of REST integrations, performance, testing, and Mendix security.
• Curiosity about AI and LLMs. MCP experience helps, but you can learn it here.
• You explain technical things to support colleagues and customers in plain language.
• You pick things up without waiting to be asked.
• Nice to have: DevOps, automated deployment, HTML/CSS.
• Fluent English and/or Dutch. 

What you get

• €5,000 to €6,500 gross per month depending on experience, plus 8% holiday allowance.
• €1,500 a year for learning, Mendix certifications included.
• €120 net per month expense allowance.
• A laptop.
• Flexible hours. You plan your own day, we look at what you deliver.
• A say in the product and in where we take AI next.