Klevu - Klevu offers instant site search solution for eCommerce stores.

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

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.

Tagalys - Data driven online Merchandising for eCommerce product listing pages.

Hawk Search - Site-search engine for eCommerce platforms.