Strongly consistent backup of Mongo with Aurora at the exact same time

At my employer we use AWS Aurora DB & MongoDB Atlas hosted databases together on one application.

So we have nail biting scenarios where records are created on both and typically MongoDB points to records on Aurora that it needs. If there is some sync issue, like the data is on Mongo, but not Aurora and vice versa, this translates to terrible UXes with permission issues.

So my question is to do with backups. These systems must be snapshot at the exact same point of time. I am thinking ideally without any client usage at an early hour like 2AM, i.e. it’s brought down for a few minutes whilst snapshots are being made.

Actually I am not sure how to limit client access whilst still being able to run mongodump or an RDS snapshot. Am I missing a better approach to backup these two data stores together?

Perhaps I can take a strongly consistent backup at a certain point in time?

You might be thinking, what happens if you take a snapshot at 2AM and you lose everything at 10AM. This is acceptable RPO.