OpenSearch is described as 'community-driven, open source search and analytics suite derived from Apache 2.0 licensed Elasticsearch 7.10.2 & Kibana 7.10.2. It consists of a search engine daemon, and a visualization and user interface, OpenSearch Dashboards' and is an app in the Development category. There are more than 10 alternatives to OpenSearch for a variety of platforms, including Linux, Mac, Windows, Online / Web-based and Self-Hosted solutions. The best alternative is Grafana, which is both free and Open Source. Other great apps like OpenSearch are elasticsearch (Freemium), Kibana (Paid), MeiliSearch (Free, Open Source) and Algolia (Free Personal).
Solr is an open source enterprise search server based on Lucene search library, with XML/HTTP and JSON APIs. Its major features include powerful full-text search, hit highlighting, faceted search, dynamic clustering, database integration, and rich document handling.
Sphinx is a free software search engine designed with indexing database content in mind. It currently supports MySQL, PostgreSQL, and ODBC-compliant databases as data sources natively. Other data sources can be indexed via pipe in a custom XML format.
High-performance, full-featured text search engine library written entirely in Java. It is a technology suitable for nearly any application that requires full-text search, especially cross-platform. Apache Lucene is a open source.