ElasticSearch - Elasticsearch is an open source, distributed, RESTful search engine.
Apache Solr - Solr is an open source enterprise search server based on Lucene search library, with XML/HTTP and...
Algolia - Algolia's Search API makes it easy to deliver a great search experience in your apps & websites. Algolia Search provides hosted full-text, numerical, faceted and geolocalized search.
Citrix Gateway - Critix Gateway is a unified gateway for users that makes it easy for them to remotely access infrastructure with the help of a single sign-on across all applications.
Lookeen - Lookeen is an enterprise search and desktop search software designed for individuals and enterprises. Its key function is Outlook search.
SearchSpring - SearchSpring is an eCommerce site search tool.