Modernizing Appraisal Application ‘Flux’ for Maximum Value 

The Perfect Opportunity

For fifteen years, the ongoing development of Flux was handled by a partner. In 2024, circumstances prompted Flux Groep B.V. to bring the technology in-house, creating the perfect opportunity for modernization. “Our architecture was solid, but also dated, making innovation and adapting to new regulations increasingly complex,” says Bas Boelhouwers, CEO of Flux Groep B.V.   

A No-Nonsense Action Plan

Moving the application started with a focused knowledge transfer to the Dutch team and the onboarding of strategic partner, Xebia. Boelhouwers, “Xebia immediately understood our challenges and ambitions, and quickly put together a no-nonsense action plan to get started. Fast and with minimal risk.” Together, they launched a full-scale modernization — making the platform scalable, agile, and ready for to offer advanced capabilities like ESG reporting and sustainability analysis.

A Three-Tier Partnership

Xebia helped modernize Flux through a three-tier approach: migrating to the cloud, rebuilding the legacy monolith with cloud-native tech, and supporting organizational change.

I. A Solid Cloud Foundation

First, a Cloud Assessment helped Xebia identify risks and opportunities in Flux’s architecture. “It gave us a solid case for cloud migration and a clear modernization roadmap,” says Michiel van Oudheusden, Lead Consultant at Xebia. These findings were presented to the board, and with Xebia’s support, Flux was successfully migrated to a solid AWS foundation by the start of 2024.

"Today, we are running a range of Microsoft technologies on top of AWS,” Van Oudheusden explains. “As we continue to modernize Flux, the benefits of cloud technology are becoming clearer by the day. For example, we can plan for peak usage, dial things down during quieter periods, and store data at significantly lower cost. We’re also doing all this with less operational effort, as the required skill set hasn’t grown — just shifted. And we made sure the team is fully trained."

II. Application Modernization

Flux's most significant shift is from a monolithic application to a cloud-native, domain-driven architecture. Van Oudheusden, “We divided the application into multiple domains, like valuations and CRM, and authentication and logging. For each domain, we build components ourselves, or we use proven technology. The result is a much leaner application focusing entirely on its core task: supporting the appraiser.” Boelhouwers adds, “Separating workflows, data, and calculation means that when something changes in one domain, we can adjust without impacting the entire application.” He continues, “This new structure improves flexibility and supports scalability. It’s a foundation built for future growth.”

GitHub played a key role in modernizing Flux. "GitHub helped us automate much of the process documentation, speeding things up and adding traceability, auto-generated records, and a clear pipeline to production — all of which support ISO compliance,” says Van Oudheusden. He continues, “Last but not least, we are also developing the front-end. Following the Strangler Fig pattern, we are gradually phasing out the old and introducing the new, one piece at a time.”

III. Adding Value Across the Organization

As Flux modernizes, so does the organization behind it. Boelhouwers, “This change isn’t isolated. Our commercial and valuation teams shifted to a more agile, customer-focused way of working, while management prioritized team and culture development. Crucially, we also gained full support from the NVM, as the app is vital to many of its members.” Van Oudheusden on Xebia’s role, “Together, we explored a fresh strategic direction: where do you want to go, and how will you get there? We supported the hiring and onboarding of new developers, delivered targeted training, and refined Agile, Scrum, and DevOps practices.”

The result? A team in complete control. Van Oudheusden, “With extensive monitoring and a streamlined release process, the Flux team now has full ownership of the platform. Deploying faster, reacting quicker, and continuously improving.” Boelhouwers adds, “Testing and releasing used to take days. Now, it’s fast. We can run multiple versions in parallel, and if something goes wrong, we know how to recover quickly.”

Finally, this shift also transformed talent attraction. “One of our biggest challenges was to hire developers who wanted to work with outdated technology or a custom legacy codebase,” says Van Oudheusden. “Now, working with new tools, attracting top talent is no longer an issue.”

The Future Shines Bright for Flux  

At present, Flux is running smoothly on AWS while its modernization is in full swing. Reflecting on the collaboration, Boelhouwers says, "The dedication and commitment of the Xebia team are amazing. Even the Managing Director of Xebia Microsoft Services got involved, applying his expertise to help resolve a complex issue.” He adds, “What really sets Xebia apart is its people. They are fully invested in both the product and the project, making them an absolute pleasure to work with.” 

By the end of 2025, Xebia plans to step back, having achieved significant results together with Flux Groep B.V., including:  

• A successful transition to AWS, laying the groundwork for scalability, flexibility, and innovation.  
• From legacy to lean: a clean, modern application ready for the future. 
• A modernized backend — automated, accelerated, secure, and compliant — giving the team complete control over its infrastructure and operations.  
• A streamlined, modern development lifecycle with updates rolling out every two weeks instead of just three times a year.  
• A mature DevOps organization, where teams own and manage all phases of development 
• An improved user experience is enabled by feedback-driven development, real-time insights, and responsive on-call support.  
• A strong foundation for an Engineering Culture built on DevOps, Agile, and a mindset geared towards continuous improvement.