Based on the Lucene library, Elasticsearch provides search capabilities. It provides a distributed, multitenant-capable full-text search engine with an HTTP web interface and schema-free JSON documents. The diagram above shows the outline.

Features of ElasticSearch:

• Real-time full-text search
• Analytics engine
• Distributed Lucene

ElasticSearch use cases:

• Product search on an eCommerce website
• Log analysis
• Auto completer, spell checker
• Business intelligence analysis
• Full-text search on Wikipedia
• Full-text search on StackOverflow

The core of ElasticSearch lies in the data structure and indexing. It is important to understand how ES builds the term dictionary using LSM Tree (Log-Strucutured Merge Tree).