The User and Address data is a one-to-many relationship. A user can have, in general, 1 to 3 ( a small number) addresses. In MongoDB, this is modeled by embedding the address data into the user data.
It is unusual, to create two collections one for each of the user and the address - especially when the addresses are going to be a very small number, and the kind of data being stored. The document structure would be something like this in a "user" collection:
Note the address is an array type field, with multiple address elements.
The two Java POJOs are the User and the Address. The User class will have a property called as address of type List<Address>. Using Spring-Data APIs for MongoDB, the CRUD operations can be performed on the "user" collection. For example, using MongoTemplate class: