Mongo (from "humongous") is a high-performance, open source, schema-free document-oriented database. MongoDB is written in C++ and offers the following features:

* Collection oriented storage: easy storage of object/JSON-style data
* Dynamic queries
* Full index support, including on inner objects and embedded arrays
* Query profiling
* Replication and fail-over support
* Efficient storage of binary data including large objects (e.g. photos
and videos)
* Auto-sharding for cloud-level scalability (currently in early alpha)
* Commercial Support Available

A key goal of MongoDB is to bridge the gap between key/value stores (which are fast and highly scalable) and traditional RDBMS systems (which are deep in functionality).