Not sure if Mongo has this feature, but in many classic SQL databases, per-user views can be created which act like tables, but are actually "the user's view in

Not sure if Mongo has this feature, but in many classic SQL databases, per-user views can be created which act like tables, but are actually "the user's view into that table". This would mean creating database user accounts on the fly for people, but it would resolve this problem (as long as the views are secure).