This document provides an overview of how MySQL helps power Web 2.0 technologies and companies. It discusses key characteristics of Web 2.0 like harnessing collective intelligence and leveraging user participation. It also examines how specific Web 2.0 applications and sites like Wikipedia, Flickr and Second Life use MySQL to store and access user-generated content at large scale in a cost-effective manner. Finally, it outlines how MySQL's features for replication, high availability and query caching enable Web 2.0 applications to scale out elastically on low-cost commodity hardware.