Imagine I'm running an MMO game where users can store arbitrary items in a stash, and then search for them based on various criteria. I would like to implement

Imagine I'm running an MMO game where users can store arbitrary items in a stash, and then search for them based on various criteria. I would like to implement this stash as a Mongo DB instance for each user, and translate the user searches into MongoDB queries. Am I offering MongoDB as a service to my users, or using it as a DB?