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Introduction to MongoDB

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Welcome to MongoDB. This document provides a brief introduction to MongoDB and some key concepts. See the installation guides for information on downloading and installing MongoDB.

What is MongoDB

MongoDB is an open-source document database that provides high performance, high availability, and automatic scaling.

Document Database

A record in MongoDB is a document, which is a data structure composed of field and value pairs. MongoDB documents are similar to JSON objects. The values of fields may include other documents, arrays, and arrays of documents.

A MongoDB document.

The advantages of using documents are:

  • Documents (i.e. objects) correspond to native data types in many programming languages.
  • Embedded documents and arrays reduce need for expensive joins.
  • Dynamic schema supports fluent polymorphism.

Key Features

High Performance

MongoDB provides high performance data persistence. In particular,

  • Support for embedded data models reduces I/O activity on database system.
  • Indexes support faster queries and can include keys from embedded documents and arrays.

High Availability

To provide high availability, MongoDB’s replication facility, called replica sets, provide:

  • automatic failover.
  • data redundancy.

A replica set is a group of MongoDB servers that maintain the same data set, providing redundancy and increasing data availability.

Automatic Scaling

MongoDB provides horizontal scalability as part of its core functionality.

  • Automatic sharding distributes data across a cluster of machines.
  • Replica sets can provide eventually-consistent reads for low-latency high throughput deployments.