At GameAnalytics we receive and process real time behavioural data from more than 100 million daily active users, helping thousands of game studios and developers understand user behaviour and improve their games. In this talk, you will learn how we managed to migrate our legacy backend system from using an in-house built streaming analytics service to Apache Druid, and the lessons learned along the way. By adopting Druid, we have been able to reduce development costs, increase reliability of our systems and implement new features that would have not been possible with our old stack. We will provide an overview of our approach to schema design, segments optimization, creation of our query layer, caching and datasources optimisation, which can help you better understand how you can successfully use Druid as a key component on your data processing and reporting infrastructure.