This book presents the theoretical foundations of organizing big data systems and explains how they are implemented in practice. It discusses the lambda architecture for building such systems, and using a specific web application as an example, it explains the features of implementing all levels of this architecture using tools like Hadoop, Cassandra and Storm. Reading this book does not require prior familiarity with the specifics of analyzing large-scale data or databases such as NoSQL, although it is useful to know about traditional databases.