Add rate limiting for backup

**Description**
Currently config lacks proper caching support.

**Proposed solution**
Add configurable caching with sensible defaults.

**Priority**: Low/Medium

The issue provides no file, test, or entry point. First reconcile the title's request for backup rate limiting with the body’s proposal for configurable caching, then locate the backup and configuration code. Done should mean the agreed behavior, configuration shape, and sensible defaults are documented and covered by appropriate tests.

Written by the indexing model from the issue text.