OpenSearch

A distributed search and analytics engine for large indexes, developed as an Apache 2.0 fork of Elasticsearch and paired with OpenSearch Dashboards for log exploration and observability. It stores documents as JSON, spreads indexes across a cluster of nodes, and adds full-text queries, aggregations, alerting and vector search on top of a distributed Lucene core.

Organisations use it for log analytics, application monitoring and product catalogues.

Running it on your own servers keeps queries, logs and documents inside a system you administer, without per-node or per-user licence costs; index snapshots provide a clear restore path.