There are also also many use cases where you don't want to "store" something at all, just compute the value (eg: a shopping cart that is not yet a purchase), an

There are also also many use cases where you don't want to "store" something at all, just compute the value (eg: a shopping cart that is not yet a purchase), and you don't want to to either 1. duplicate implementations or 2. wait for a network request to your database to complete.