About Chaïm
Chaïm Zonnenberg
Senior .NET developer with 20+ years of experience. Specialised in AI integration, Identity/SSO and generative AI development for enterprise and SaaS teams.
Senior .NET developer with 20+ years of experience. Specialised in AI integration, Identity/SSO and generative AI development for enterprise and SaaS teams.
I'm Chaïm, 44 years old, married and father of two. I live in De Bilt near Utrecht, The Netherlands. When I'm not behind my screen, I enjoy hiking and playing board games with the kids.
What drives me? I genuinely enjoy complex problems. When everyone says "that's too complicated" or "we don't have people for that", that's when I get energised. I can't sit still when there's a problem that can be solved.
I've been programming since I was seven. At sixteen, I sold my first software product to 35 customers. That combination of building and entrepreneurship never left.
I graduated with two bachelor's degrees cum laude (Computer Science and Mathematics) and a master's in Computer Science from Utrecht University. Since then, I've been building software for enterprise organisations: from financial institutions to real estate and pension management.
In 20+ years of enterprise software, I've learned that the hardest problems are rarely purely technical. It's about building the right thing, at the right time, with the right people. That's what I'm good at.
years of enterprise software experience
paying customers on own SaaS products
enterprise organisations served
"Chaïm got up to speed exceptionally fast and consistently made the right decisions based on his deep knowledge of .NET and SQL Server."
Cees, Software Architect at multinational
I've been working with teams that hit the same walls for years. This is what I keep hearing:
"Our competitor already has a chatbot. The board is asking when we'll follow. But nobody on the team has AI experience, and I need to explain it at the next steering committee."
"Our enterprise client demands SSO and SCIM. The deal is under pressure. Every week of delay costs us trust, and possibly the contract."
"We need a senior developer who hits the ground running. Not someone who needs three months to understand the codebase, while the roadmap is screaming for results."
"Our technical debt keeps growing. Every sprint we push the complex problems to next time. Surely we shouldn't keep kicking the can down the road forever?"
I recognise that pressure. At ABN AMRO, PGGM and Van Lanschot I've seen from the inside how teams struggle with missing specialist knowledge. It doesn't have to be that way. With the right person on board, you can achieve in weeks what otherwise takes months.
At seven, we had a Microsoft MSX computer at home. Not to play games. I wanted to understand how it worked. A year later I was writing my first programs. At sixteen, I sold software to 35 customers. Building and entrepreneurship were in my DNA from the start.
After two bachelor's degrees cum laude (Computer Science and Mathematics, Utrecht University), I started at DTZ Zadelhoff, where I quickly grew from developer to data manager. Then came Kadenza, where I worked on complex valuation models.
In 2011 I made the choice: go freelance. Not to earn more, but to choose which problems I work on. Since then I've taken on major assignments at ABN AMRO, PGGM and Van Lanschot, as developer, architect and project manager. The complex, specialist challenges where teams get stuck, that's what drives me.
In 2019 I built Factuur-Assist.nl, an invoicing platform that now has 135+ paying customers. Not as a side project, but as proof that I can build, launch and maintain complete products for years.
Today I build with the same tools I deploy for clients. This website? Built with Claude Code. I use daily what I can implement for your team.
Is your team stuck on AI, SSO, or complex .NET features? Chances are I've solved exactly this kind of problem before. Let's see if I can solve this for your team within weeks.
"Chaïm is a true professional. One you don't want to let go from day one. Proactive is his motto. He picks up what matters and doesn't let go until it's resolved."
Robert, IT Team Lead at financial institution
Tell me about your situation. I'll give you an honest assessment: whether I'm the right person, and how I'd approach it.