Nextail: How a Spanish Startup's Prescriptive AI Is Defeating Excel in Fashion Retail

In the cutthroat world of fast fashion, where trends are born and die in weeks and the wrong size in the wrong store can mean the difference between selling at full price or slashing margins in clearance sales, there's an uncomfortable truth the industry has taken decades to accept: the most critical business decisions—what to ship, where, and when—are still being made with spreadsheets, gut feeling, and mental maps. This is the story of Nextail, a Madrid-based startup founded in 2014 by a team that knew that reality from the inside and decided to destroy it with mathematics. It is a case study of how prescriptive analytics and stochastic optimization are replacing Excel in an industry worth billions. The Origin: When Zara Wasn't Enough Nextail's genesis is directly linked to the epicenter of global fast fashion. Joaquín Villalba, an industrial engineer from the Universitat Politècnica de València with an MBA from INSEAD, served as European Logistics Director at Zara-Inditex, where he