From expert tool to scalable SaaS

The client

Resourcefully is an Amsterdam-based energy transition consultancy that helps municipalities, businesses, and housing developers make smarter, data-driven decisions about energy. They develop FLEX+: a simulation and advisory tool that models energy flexibility, grid congestion, and future energy scenarios. From individual buildings to entire neighbourhoods. It was built as an expert tool. We helped turn it into a product. 

The challenge

Resourcefully wanted to make FLEX+ commercially viable beyond project-based consulting. Accessible to a wider audience, deployable at scale. The core simulation logic existed. What was missing was the product layer: interfaces, workflows, user management, and a solid architecture. And it needed to be built fast enough to validate assumptions before over-investing in the wrong direction.

The solution

We applied spec-driven development: before writing a single line of product code, we built a living specification inside the codebase. Accessible to both developers and AI agents at all times. Specifications are not a way to predict the future. They’re a way to explore it.

We developed feature specs collaboratively, refined with AI assistance, and only implemented them after automated validation. We resolved bugs with Red-Green-Refactor cycles. Misalignments triggered spec updates, instead of patches. With Resourcefully next door on the Marineterrein, we could course-correct quickly and keep the build moving.