As per the mongorestore
- to preserve UUID must use drop collection
- if the collection is dropped then it will affect user/login access.
This cascading effect makes it's impractical to use. We wanted to use mongorestore UUID as an idempotent operation, in case halfway things go wrong and have to start again then it's useful to preserve UUID.
Also, in the mongorestore there should be an option to ignore/skip index creation, we were trying to bring data from the legacy app without indexes. It seems that's not possible at this moment.