Stores search-optimized representation of the data.
Documents = JSON data Index = Collection of documents Mapping = Schema of the index. You can add whatever data you want in the document, but the mapping defines what data is searchable.
The Elasticsearch query syntax is very similar to that of SQL, and it's also JSON based which makes it very easy to work with.
Apache Lucene, the highly optimized low-level search library.
Elasticsearch handles the distributed systems aspects: cluster coordination, APIs, aggregations, and real-time capabilities while the "heart" of the search functionality is handled by Lucene.
A simple query might be to search for books with "Great" in the title:
// POST /books/_search
{
"query": {
"match": {
"title": "Great"
}
}
}