Elasticsearch

Elasticsearch is a distributed search and analytics engine built on Apache Lucene, storing JSON documents in inverted indexes that make text matching fast across many nodes. It handles full-text search, fuzzy matching, aggregations, and vector similarity, and results come back ranked through a JSON query DSL.

Applications use it for site and product search, log exploration, and relevance ranking, usually paired with dashboards for investigating the same documents.

Putting the cluster in KibanOS on your own servers keeps both the index and the logs it holds inside your perimeter, with no seat count to negotiate.