Elasticsearch is a search engine based on the Lucene library. 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.
Where to Learn ???
Here are some links so you can learn Elasticsearch free,
- Codemy School (YouTube)
- Hans Schenker bei (YouTube)
- Jayendra Singh Collection (YouTube)
- Media.com
- Techie Life Style (YouTube)
If you know other sites that are free, Fell free to add to the comment section.