Elasticsearch & the Elastic Stack
Understand the distributed search engine at the core of the ELK stack.
Elasticsearch is a distributed, document-oriented search and analytics engine built on Apache Lucene, and it is the heart of the Elastic (ELK) Stack. Data is stored as JSON documents in indices; each index is split into shards (primary and replica) spread across nodes, which is how Elasticsearch scales horizontally and stays available when a node fails. The defining feature is the inverted index: every term is mapped to the documents containing it, making full-text search and aggregations extremely fast.
The index at the back of thousands of books merged into one: instead of reading every page, you look up a word and instantly get every page it appears on, across the whole library.