I’m new to MongoDB.

In one of the answers to this question MongoDB – What about Decimal type of value?, there’s a recommendation from Philipp1:

you shouldn’t do any business logic on the database anyway, especially not when it’s a “dumb” database like MongoDB

I also read that MongoDB is not a transactional database, and transactional operations (https://www.mongodb.com/docs/manual/core/transactions/) should be avoided.

Then my question: where should my business logic be? Something simple as: add $5.00 to the account balance.

Thank you very much!