/ˈmɒŋɡoʊ diː biː/
n. — "NoSQL dumpster storing JSON blobs without schema nagging."
MongoDB is document-oriented NoSQL database using BSON (Binary JSON) format to store schema-less collections of records, grouping related documents without rigid table schemas or foreign key joins. Unlike SQL RDBMS, MongoDB embeds related data within single documents or references via ObjectIDs, supporting ad-hoc queries, horizontal sharding across replica sets, and MapReduce aggregation pipelines.
Key characteristics and concepts include:
- BSON documents with dynamic fields, embedded arrays/objects avoiding multi-table JOIN hell.
- Automatic sharding distributing collections across clusters using shard keys for horizontal scaling.
- Replica sets providing primary→secondary failover, eventual consistency across distributed nodes.
- Aggregation framework chaining $match/$group/$sort stages, mocking SQL GROUP BY limitations.
In write workflow, application embeds user profile/orders into single document → mongod shards by user_id → primaries replicate to secondaries → aggregation pipeline computes daily sales across shards.
An intuition anchor is to picture MongoDB as a filing cabinet with expandable folders: stuff complex JSON trees anywhere without predefined forms, search by any field, shard across drawers—chaotic freedom vs SQL's rigid spreadsheet prison.