Handle edge cases in filtering

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

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

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

The issue names no files, tests, or entry points. Start by locating the middleware configuration and existing option handling, then determine how backup is expected to behave and where its default should be verified; done means the new option is supported with a default of false and the requested middleware backup behavior is covered.

Written by the indexing model from the issue text.