Problem:
- Cache::remember() does not cache null return values
- When no FQDN was configured, the closure returned null
- This caused DB queries on every request, defeating the cache
Solution:
- Use empty string ('') as sentinel value instead of null
- Convert sentinel back to null after retrieving from cache
- Now both positive and negative results are cached properly
Changes:
- Return empty string from closure instead of null
- Add explicit sentinel-to-null conversion after cache retrieval
- Add test to verify negative caching works correctly
This ensures zero DB queries even when FQDN is not configured.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
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