Database structure help and how to connect between different collections

Hi all. I’m new to databases in general. I have a Node+Express multiuser app with each user’s data and login credentials in mongodb Altas database.
So I thought of the following structure -

App Database
Accounts Collection - To store only username and password
Profile Collection - to store all other information related to the user

I don’t know how to relate one to another. one option I can see is to have username in both profile and account document for every user. Then I can check password using the account document and if successful, I would search the username in Profile collection and return the data in a response.
Or am I thinking too hard and I should just store both username, password, and profile data in one document for each user.

What’s the best practice?

I realise this information must be somewhere in the documentation but I kinda have to sumbit a fullstack prototype tomorrow so would really appreciate if someone could point me in the right direction

We never think too hard. B-)

But since

put everything in the same collection. MongoDB is flexible enough that you can revise your schema later.

In the mean time enjoy some reading: