Document databases

A document-oriented database is suitable for documents and semi-structured data. The central concept of a document-oriented database is the notion of a document. Documents encapsulate and encode data (or information) in some standard formats or encodings such as XML, JSON, and BSON. Documents do not adhere to a standard schema or have the same structure, so they provide a high degree of flexibility. Unlike relational databases, changing the structure of the document is simple and does not lock the clients from accessing the data.

Document databases merge the power of relational databases and column-oriented databases. They provide support for ad hoc queries and can be scaled up easily. Depending on the design of the document database, MongoDB is designed to handle a huge amount of data efficiently. On the other hand, CouchDB provides high availability even in the case of hardware failure.