Decide when MongoDB documents should contain related data and when that data should live somewhere else.
MongoDB's flexible document model gives you more than one way to represent relationships. You can embed related data inside a document or store references to documents in another collection.
The right choice depends on how your application reads and updates data. Embedding can make related reads simple and fast, while referencing can make sense when data is large, shared, or updated independently. Good MongoDB modelling starts with the application's access patterns rather than trying to copy a relational database design directly.
What you'll walk away knowing