1. Elasticsearch concepts
What Wikipedia says
Elasticsearch is a search engine based on Lucene. It provides a distributed, multitenant-capable full-text search engine with an HTTP web interface and schema-free JSON documents. Elasticsearch is developed in Java and is released as open source under the terms of the Apache License. Official clients are available in Java, .NET (C#), PHP, Python, Apache Groovy, Ruby and many other languages. According to the DB-Engines ranking, Elasticsearch is the most popular enterprise search engine, followed by Apache Solr, also based on Lucene.
Source: Wikipedia – Elasticsearch
Definition from the Elastic site
Elasticsearch is a real-time distributed search and analytics engine. It allows you to explore your data at a speed and at a scale never before possible. It is used for full-text search, structured search, analytics, and all three in combination.
Source: Elastic – Getting Started
Real-world examples:
- Wikipedia uses Elasticsearch for full-text search with highlighted snippets, plus search-as-you-type and did-you-mean suggestions.
- The Guardian combines visitor logs with social-network data to give editors real-time feedback on the public's response to new articles.
- Stack Overflow combines full-text search with geolocation queries and uses more-like-this to find related questions and answers.
- GitHub uses Elasticsearch to query 130 billion lines of code.