Glossary

Term Definition
capped collection A fixed-sized collection that automatically overwrites its oldest entries when it reaches its maximum size.
oplog A capped collection that stores an ordered history of logical writes to a MongoDB database. The oplog is the basic mechanism enabling replication in MongoDB.
path (JSON document path) The required sequence of keys to access one specific value of the document (for example, address.zipcode)
replica set A replica set is the way provided by MongoDB to add redundancy to survive network partitions and other technical failures (more info)
sharding When the amount of data is too large it is recommended to distribute the information across multiple machines, this is known as sharding in MongoDB (more info)