Excessive cache invalidation

Problem Summary

Excessive cache invalidation defeats the purpose of caching by clearing the cache too often. Each invalidation forces regeneration from the origin, eliminating performance benefits.

Performance Impact

Low cache hit ratio: Cache rarely serves content
Constant regeneration: Origin generates same content repeatedly
No performance benefit: Effectively no caching
Increased server load: More origin requests

How to Detect

CDN dashboard: Very low cache hit ratio
Server logs: High cache purge frequency
Monitoring: Cache invalidation alerts

Solutions

1. Set Appropriate Purge Rules

Only purge when content actually changes.

2. Use Stale-While-Revalidate

Code

Cache-Control: public, max-age=3600, stale-while-revalidate=86400

3. Smart Purging

Purge specific URLs, not entire cache.

4. Increase Cache TTL

Longer cache duration between invalidations.