:Why is the cache hit ratio of a CDN POP decreased?

A cache hit ratio drop is typically caused by one of the following four scenarios. Check each one to identify the cause.

• You recently refreshed cached resources. Refreshing forces the POP to discard its cached copies and pull fresh content from the origin server. The hit ratio drops temporarily while the POP rebuilds its cache from incoming requests. No action is needed — the ratio recovers as traffic warms the cache.

• A sudden bandwidth spike occurred. When traffic surges unexpectedly, the POP cannot serve all requests from cache because many requests target resources that have not been cached yet at that scale. The POP sends more back-to-origin requests, pulling the ratio down. Once traffic stabilizes and the cache warms to the new traffic pattern, the ratio climbs back. If spikes are recurring, consider using cache prefetch to pre-populate the POP with your most-requested resources before traffic peaks.

• The POP is receiving requests for uncached content. If users are requesting URLs the POP has never cached — new content, low-traffic resources, or content with very short TTLs — every request goes back to the origin server. Check whether your cache TTL settings are configured. A TTL that is too short (or set to 0) causes the POP to treat all content as expired. Increase the TTL for static assets to allow repeated requests to be served from cache. Also verify that your origin server's Cache-Control header is not set to no-cache, no-store, max-age=0, or private — any of these values prevents the POP from caching the response.

• You modified the cache policy. Changing the cache policy — for example, updating TTL values, modifying which headers are used as cache keys, or switching caching rules — causes the POP to invalidate existing cached content and re-fetch from the origin server. The ratio dips while the cache rebuilds. No immediate action is needed unless the new policy is misconfigured. Verify that the updated policy matches your intended caching behavior and that TTL values are appropriate for your content types.