This document discusses using a reactive lambda architecture with open source tools to solve real-time big data problems. It begins by defining big data and explaining that simply having data is not enough - you need to solve the right problems with the right team and tools. It then presents three example problems that could benefit from real-time big data solutions: disaster prediction and response, understanding customers through social media data, and optimizing marketing campaigns in real-time. The document proposes using a reactive lambda architecture along with open source frameworks like Hadoop, Spark, Storm and databases like Redis, HDFS and HBase to build streaming data pipelines and query data in real-time. It demonstrates this through a social media user tracking and personalized recommendations use