Document databases focus on storage and access optimization
for documents as opposed to rows or records. The document
database entities are just records with multiple fields. All of
the current document databases support documents in JSON
(JavaScript Object Notation) format.
Some document databases are BigTable databases, others provide
MapReduce processing, while some of them are columnar
databases. The inference is that the storage and access implementation
is independent of the database’s orientation towards
document-oriented databases. Some document databases provide
added capabilities such as SQL or SQL-like query processing capabilities.
For instance, Terrastore document store provides advanced
scalability and elasticity features without sacrificing Consistency