The book describes most of the modern open source databases: Redis, Neo4J, CouchDB, MongoDB, HBase, PostgreSQL and Riak. For each database, examples of working with real data are given, demonstrating the main ideas and strengths. This book will shed light on the strengths and weaknesses of each of the seven databases and teach you how to choose the one that better fits the bill. The publication is intended for programmers of various qualifications who use databases in their professional activities.