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.
ProppyJS - Functional props composition for UI components (React & Vue)
Google Custom Search - Google Custom Search enables you to create a search engine for your website, your blog, or a collection of websites.
Appbase.io - Search stack for building modern apps
ElasticSearch - Elasticsearch is an open source, distributed, RESTful search engine.
Deja vu - A mind-blowing interactive piece to promote an album. Wow.