MongoDB is a document database offering high performance, easy scalability and high availability. It is a cross-platform document-oriented database. It is classified as a NoSQL and makes the integration of data in certain types of applications faster and easier. MongoDB is free and open-source software and has been released under a combination of the Apache License and the GNU Affero General Public License.

Rather than taking a business subject and breaking it up into multiple relational structures, MongoDB stores the business subject in the minimal possible document numbers. For example, rather than storing  author and title information in two distinct relational structures, author, title and other title-related information may all be stored in a single document known as Book, which is much more easier to work with and intuitive. MongoDB supports search by range queries, field, and regular expression searches. Queries can include user-defined JavaScript functions and also return specific fields of documents.

MongoDB has been adopted as backend software by various major websites and services which include eBay, Craigslist, Foursquare, Viacom, SourceForge and the New York Times, among others. MetLife employs MongoDB for “The Wall", a customer service application offering a "360-degree view" of MetLife customers. Sourceforge employs MongoDB for its back-end storage pages. SAP uses it in the SAP PaaS. It is used by Shutterfly for its photo platform. The photo platform stores 18 billion photos uploaded by 7 million users of Shutterfly as of 2013. It has been deployed as the primary back-end for the Data Aggregation System for the Large Hadron Collider by the the Compact Muon Solenoid at CERN. Foursquare deploys MongoDB on Amazon AWS for storing venues and user check-ins into venues. Sophos employ it in their cloud security technology. EBay uses MongoDB in the internal Cloud Manager State Hub and in the search suggestion. No wonder, MongoDB  is considered to be the most popular NoSQL database system.

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