How do you monitor performance for one of your clients on a specific user segmentation when dealing with billions of events a day ? With over 2 billion ads served and 230Tb of data processed a day, we at Criteo have a comprehensive need for an interactive analytics stack. And by interactive, we mean a querying system with dynamic filtering to drill down over multiple dimensions, answering within sub-second latency. This session will take you on our journey with Druid, ""an open-source data store designed for real-time exploratory analytics on large data sets"". We will walk attendees through Druid's architecture and noticeable concepts, how relevant they are for some use cases and how it really performs.