elasticsearch!

Algolia provides a developer-friendly RESTful API for website and app instant search. Most web services and mobile apps, such as Spotify, Salesforce or Amazon need to provide a fast and meaningful access to database objects via a simple search box. People want to find songs, invoices, products in just a few keystrokes.

Solr is an open source enterprise search server based on Lucene search library, with XML/HTTP and JSON APIs. Its major features include powerful full-text search, hit highlighting, faceted search, dynamic clustering, database integration, and rich document handling. Providing distributed search and index replication, Solr is highly scalable.

Xapian is an open source probabilistic information retrieval library, released under the GNU General Public License (GPL). It is a full text search engine library for programmers. It is written in C++, with bindings to allow use from Perl, Python, PHP, Java, Tcl, C#, Ruby, and Lua. Xapian is highly portable and runs on Linux, Mac OS X, FreeBSD, NetBSD, OpenBSD, Solaris, HP-UX, Tru64, IRIX, Microsoft Windows, GNU Hurd, and OS/2.

OpenSearchServer is an open source application server allowing development of index-based applications like search engines. Main features of OpenSearchServer are : An integrated crawler for databases, web pages and rich documents; a user friendly GUI allowing development of most applications with some clicks through an interface built in Zkoss; snippets; faceting; an html renderer for integrating search results in a page; and monitoring and administration features.

Whoosh is a fast, featureful full-text indexing and searching library implemented in pure Python. Programmers can use it to easily add search functionality to their applications and websites. Every part of how Whoosh works can be extended or replaced to meet your needs exactly.

Unlimited Searching

Cludo is a powerful search solution to your website. It is built on top of Elasticsearch which means you do not have to do any further developing, or hire any developer concerning site search. Cludo's focus is to deliver an easy to use search engine with the greatest support and tools.

Measured Search provides a fully-managed personalized search & discovery service offering feature packed textual & relevance based search, contextualized recommendations combined with search & interaction analytics that enable you to increase conversions, interactions & user-satisfaction.

SearchBlox is an out-of-the-box Enterprise Search Solution built on top of Apache Lucene/Solr. It is fast to deploy, easy to manage and available for both on-premise and cloud deployment.

Manticore Search is a feature-rich search engine that is blazing fast, reliable and scalable. It is 100% open source project started as a fork of Sphinx Search.

Expertrec site search engine helps you add ultra fast search to your website . It adds a superb autosuggest and search listing pages where people can find products with a few keystrokes. Along with this you get complete control over your search results with complete merchandising options and access to real time search analytics.

Elasticlunr.js, lightweight full-text search engine in Javascript for browser search and offline search. Elasticlunr.js is developed based on Lunr.js, but more flexible than lunr.js. Elasticlunr.js provides Query-Time boosting and field search. A bit like Solr, but much smaller and not as bright, but also provide flexible configuration and query-time boosting.

Historically, software platform vendors have created lock-ins for customers that building on their stacks. Open source has provided greater freedom and reduced investments for applications projects. The so-called Platform As A Service (PaaS) offerings from the cloud providers pose a new threat, creating new lock-in situations.

Vespa is an engine for low-latency computation over large data sets. It stores and indexes your data such that queries, selection and processing over the data can be performed at serving time.