The scenario ¶
You have different collections in MongoDb with de-normalized attributes. As you may know, due to its not-join nature, MongoDb tends to encourage repetition of the same value in different collections (de-normalization). In this MongoDb is opposed to a more SQL-like approach where you usually reference only the ID of the value with a foreign key.
In SQL-like DBs ¶
For example this scenario applies to a SQL-like approach: