Elasticsearch is an open source search and analytics engine that can run in a distributed environment. It provides RESTful APIs to ingest and retrieve high-volume, high-velocity data. Elasticsearch is built on top of Apache Lucene and was released in 2010. It has popular use cases such as:

• Log analytics
• Full-text search
• Operational and business intelligence
• Distributed Document Store

Elasticsearch can store new data in the form of documents and it indexes the documents in a cluster by adding searchable references to the document. This enables faster searching for and retrieval of high-volume, velocity documents. 

This chapter will use Elasticsearch to store and retrieve blog articles because of the search and indexing capabilities it provides; a blogging system is expected to have a lot of text, which needs to be searched very quickly to provide a good user experience.