How to link schemas in mongodb?

Question

MongoDB

What I need? For example, there are two schemas user and post. I want to build the following relationship between them: I save the user ID in the post - postModel.create (data), and when I then make a request to the user - userModel.findById (id), I want to get, among other information about the user, the posts field, which will contain information about the previously saved post of this person.

I know that you can save posts directly to the user model and make a link in the schema in the form
[{type: mongoose.Schema.Types.ObjectId, ref: 'Posts'}], but I don't want to access the user model every time I update posts (Or is this the only way in my case?) - I want to access the post model and then see the changes in the user.

I don't have much experience with mongo, I don't understand how to humanly connect these schemas.