Mongoose schemas not picking up new properties

I have this mongoose schema, I added updated_by and created_by, but for some reason when I save models from client to server, those fields aren't visible:

   userSchema = mongoose.Schema({
            role: {
                type: String,
                enum: ['Admin', 'Owner', 'User']
            },
            username: {
                type: String,
                unique: true,
                required: true,
                validate: [validation.usernameValidator, 'not a valid username']
            },
            passwordHash: {
                type: String,
                required: true,
                validate: [validation.passwordValidator, 'not a valid password']
            },
            email: {
                type: String,
                unique: true,
                required: true,
                validate: [validation.emailValidator, 'not a valid email address']
            },
            firstName: {
                type: String,
                required: false
            },
            lastName: {
                type: String,
                required: false
            },
            registered_at: {
                type: Date,
                default: Date.now
            },
            created_by: {
                type: String,
                required: false
            },
            updated_by: {
                type: String,
                required: false
            },
            created_at: {
                type: Date,
                default: Date.now
            },
            updated_at: {
                type: Date,
                default: Date.now
            }
        },
        {
            autoIndex: false
        });

is this normally a problem? Do I have to somehow rebuild something with Mongoose or MongoDB in order for them to pick up the new properties on this model?

Of course, I did restart the mongoDB server, but that didn't do anything.

In any case, if you save your User model, the fields with actual values shown in MongoDB will be the ones you set a value for yourself when saving the model OR the fields with a default value set in your userSchema.

So, just to clarify on this:

    address: { type: String, default: ' ' } 

will be shown in MongoDB with a value of ' ' unless you set a specific address when saving your User model.

But,

    address: String

will NOT be shown in MongoDB unless you set a specific address when saving your User model.

EDIT Thanks to Matthew for pointing it out, actually upsert behavior is indeed the following:

If upsert is true and no document matches the query criteria, update() inserts a single document.