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.
FYI - Find your documents, like magic 🔮
Apache Solr - Solr is an open source enterprise search server based on Lucene search library, with XML/HTTP and...
Findo - Your smart search 🔍 assistant across personal cloud ☁️
ElasticSearch - Elasticsearch is an open source, distributed, RESTful search engine.
Vaultedge - Access all your documents in one place.