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.
Meta Search - Search your Desktop, Google Drive, Dropbox, Gmail, Evernote.
ElasticSearch - Elasticsearch is an open source, distributed, RESTful search engine.
Google Cloud Search - Search across all your company's content in G Suite.
Swiftype Site Search - Swiftype Site Search helps to sell more, get the right answer to more people on the platform and surface relevant content for readers and followers.
Vaultedge - Access all your documents in one place.