Mongo DB

MongoDB is a document-oriented database that stores data as BSON (Binary JSON) documents rather than rows in relational tables. 10gen (now MongoDB, Inc.) released it in 2009, initially as part of a platform-as-a-service product before open-sourcing the database as a standalone project. Documents in a collection can have different fields, making schema changes straightforward compared to ALTER TABLE operations in relational databases.

The current stable release is MongoDB 8.0. The aggregation pipeline handles complex queries through a sequence of transformation stages rather than SQL joins. MongoDB supports replica sets for high availability and sharding for horizontal distribution of data across machines. MongoDB Atlas is the managed cloud offering, available on AWS, Azure, and Google Cloud. The server source code is licensed under the Server Side Public License (SSPL).

The official manual covers data modeling, query optimization, and operations. The source code is on GitHub.