This document discusses how Shein uses data and algorithms to disrupt the fast fashion industry. It summarizes that Shein uses an engagement algorithm in its app to gather data on customer preferences and only produces items that generate high engagement. This allows Shein to produce smaller batches tailored to customer needs with less capital and faster production. The document advocates that companies flip their production model to first generate customer data and then produce items, with the user experience designed to optimize data generation and a self-learning algorithm that improves the experience over time.