elasticsearch is described as 'ElasticSearch is a distributed, RESTful, source-available search server based on Java under the Apache License ( Lucene )' and is a Search Server in the Development category. There are more than 50 alternatives to elasticsearch for a variety of platforms, including Online / Web-based, Linux, Mac, Self-Hosted solutions and Windows. The best alternative is Apache Solr, which is both free and Open Source. Other great apps like elasticsearch are MeiliSearch (Free, Open Source), Sphinx (search engine) (Free), Typesense (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.
Almost everyone thinks Apache Solr is a great alternative to elasticsearch.
Sphinx is a 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.
Almost everyone thinks Sphinx (search engine) is a great alternative to elasticsearch.
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.