> For the complete documentation index, see [llms.txt](https://bigdata-2.gitbook.io/bd201notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://bigdata-2.gitbook.io/bd201notes/topics-for-writiing-task/elk.md).

# ELK

* What is ELK and what it is used for?
* Describe key concepts of Elasticsearch
  * Cluster
  * Node (with types)
  * Index
  * Document
  * Shard
  * Replica
* Elasticsearch. Response format: Special Fields
* Refresh & Flush
* Document update
* Mapping/Dynamic Mapping (the text type)
* Elasticsearch API. Search Endpoint
* Elasticsearch API. Term & Term-Level Queries
* What is Kibana/Logstash/Beats?
* What is MetricBeat?