You Sun Jeong is a senior software engineer at SK Telecom who has worked on several big data projects including a Hadoop data warehouse, real-time network analytics, and a big data discovery solution. The presentation introduces Druid, an open source distributed OLAP data store designed to enable fast analytics on large datasets. Key features of Druid include real-time ingestion, in-memory columnar storage, and support for common OLAP operations like roll-ups, drill-downs, and slicing and dicing. A live demo then shows real-time ingestion and cohort analysis on a dataset of mobile app user events.