The release of Elasticsearch 2.0.0 saw a major refactoring in Elasticsearch Query DSL, the interface provided by Elasticsearch to write queries in the JSON format. Covering complete Query DSL is out of the scope of this book. But for a person who doesn't have much prior experience with a full text search engine, the number of queries exposed by Elasticsearch can be overwhelming and very confusing. So, we have decided to cover the most frequently used queries, along with making readers aware about how to use queries and filters with revised Query DSL syntax. Thus, this book can serve the purposes of both types of readers: those who are aware of old versions as well as those who are starting with version 5.0.