Is field dependency possible in mongodb?

Question

MongoDB

There is a user model with a block of his experience (xp)

...
 stats    : {
...
        xp:             { type: Number, default: 0 }
    },
...

There is a dependence of the user level on his xp. When recruiting a certain amount of xp, the user increases his level.
At the moment, I can only see the output of the level - through a template (through conditions) or through front-end scripts (which is essentially the same).
The question is how to implement user-level storage and trigger events to change the user level?

Answer 1

On the server where the function changes xp, let the level be calculated and written to the base with the same update, for the event - immediately check if the level has changed and do something, for example, send a message to the client.

Answer 2

Schemes describing the dependencies of fields, validators and limiters are built on top of the NoSQL storage, usually. In the case of MongoDB, this add-on could be Mongoose, which supports calculated fields: mongoosejs.com/docs/guide.html#virtuals .