ElasticSearch - Elasticsearch is an open source, distributed, RESTful search engine.
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.
Logz.io - Logz.io provides log analysis software with alerts, role-based access, unlimited scalability and free ELK apps. Index, search & visualize your log data!
Apache Solr - Solr is an open source enterprise search server based on Lucene search library, with XML/HTTP and...
Searchkick - Intelligent search made easy with Rails and Elasticsearch - ankane/searchkick
Google Custom Search Engine - Google Custom Search is a platform provided by Google that allows web developers to feature specialized information in web searches, refine and categorize queries and create customized search engines, based on Google Search.