Queries run against a mongoD cluster with the notablescan option turned on (referred to as "Require Indexes for All Queries" in the Atlas cluster configuration options) do not respect this option when enabled. I am able to perform both filter and sort queries against fields that are not indexed.

A very simple query against my cluster: db.posting.find({},{cd:1}).limit(1).sort({cd:1}) . cd is not indexed, though this query goes through.