MongoDB developers and DBAs work with physical clusters, machines, instances, storage systems, disks, etc. All MongoDB users, developers, and their applications work with logical entities: databases, collections, documents, fields, shards, users, and data types. There are a lot of similarities with Couchbase since both are document(JSON)- oriented databases. Let’s compare and contrast the two with respect to database objects. You may also refer back to Part 1 of this series comparing the architecture.
MongoDB Organization
A full list of MongoDB schema objects is listed here and here. A database instance can have many databases, a database can have many collections, and each collection can have many indexes. Each collection can be sharded into multiple chunks on multiple nodes of a cluster using a hash-sharding strategy or an index sharding strategy. The MongoDB indexes are local to their data. Therefore, the indexes use the same strategy as the collection it is created on.
— Homepage
Design & Dev | Paris & Co Iteration 001