Data-Warehouse on Ivan Luminaria

4 million euros, two multinationals, zero software: the true story of a failure foretold

Tue, 30 Dec 2025 08:03:00 +0100

The story I’m about to tell is true. I won’t name names — not out of diplomacy, but because names don’t matter. What matters is understanding the mechanism. Because this mechanism repeats itself, identically, in dozens of companies. And it costs millions.

🏢 The client: an insurance group with a legitimate ambition #

A solid company in the insurance sector. Operations in Italy, France, Northern European countries, Spain. Thousands of employees, millions of policies under management, a growing business.

SCD Type 2: the history the business didn't know it needed

Tue, 11 Nov 2025 08:03:00 +0100

The sales director shows up at the Monday morning meeting with a simple question: “How many customers did we have in the North region last June?”

The DWH’s answer: silence.

Not because the system was down, or the table was missing. The data was there, technically. But it was wrong. The DWH returned the customers currently in the North region — not the ones that were there in June. Because every night, the loading process overwrote the customer master data with current values, erasing any trace of what came before.

Wrong grain: when the fact table can't answer the right questions

Tue, 21 Oct 2025 08:03:00 +0100

The meeting had started well. The sales director of an industrial distribution company — around sixty million in revenue, three thousand active customers, a catalog of twelve thousand SKUs — had opened the new data warehouse presentation with a smile. The numbers matched, the dashboards were polished, the monthly totals by agent and territory reconciled with accounting.

Then someone asked the wrong question. Or rather, the right one.

“Can I see what customer Bianchi purchased in March, line by line, product by product?”