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)
ElasticSearch - Elasticsearch is an open source, distributed, RESTful search engine.
Appbase.io - Search stack for building modern apps
Site Search 360 - Site Search 360 enhances and improves your built-in CMS or product search with autocompletion, semantic search, filters, facets, detailed analytics, and a whole lot of customization options.
Reactive Search - UI components for building Amazon / Yelp like Search