Handle edge cases in sorting

**Feature request**
It would be great to have backup for models.

**Use case**
Many users need this functionality for production deployments.

**Implementation idea**
Add a new config option `enable_backup` with default `false`.

No file, test, or entry point is named. First reconcile the title's sorting reference with the body’s model-backup request, then trace how configuration options are defined and consumed; the work is done only when the backup behavior, default setting, and coverage for production use cases are clearly specified.

Written by the indexing model from the issue text.