Can we join two collections on mongo based on a unique ID and how do we keep it the same?

[The-Law-1]

https://stackoverflow.com/questions/21971666/mongoose-unique-field

[The-Law-1]

https://stackoverflow.com/questions/36805784/how-to-join-two-collections-in-mongoose/44357938

[The-Law-1]

Or, use one collection and have the data be divided in two categories, users and user preferences (distinguishable via tag ?)

[The-Law-1]

Solved, searching prefs based on username found with jwt