Elasticsearch is a highly scalable open-source full-text search and analytics engine. It allows you to store, search, and analyze big volumes of data quickly and in near real time. It is generally used as the underlying engine/technology that powers applications that have complex search features and requirements. It allows you to start with one machine and scale to hundreds, and supports distributed search deployed over Amazon EC2’s cloud hosting. For Elasticsearch Online training go here
You can also get training directly from the engineers behind the product - https://training.elastic.co/