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.
Nosto - Personalized shopping experiences for e-commerce businesses
Google Custom Search - Google Custom Search enables you to create a search engine for your website, your blog, or a collection of websites.
Tagalys - Data driven online Merchandising for eCommerce product listing pages.
ElasticSearch - Elasticsearch is an open source, distributed, RESTful search engine.
Certona - Certona is a multi-channel personalization platform for brands and retailers.