You are using Cloud CDN to deliver static HTTP(S) website content hosted on a Compute Engine instance group. You want to improve the cache hit ratio. What should you do?

Customizing cache keys to omit the protocol (HTTP vs. HTTPS) allows Cloud CDN to serve the same cached object for both HTTP and HTTPS requests, significantly improving the cache hit ratio. If the protocol is included in the cache key, Cloud CDN treats http://example.com/image.jpg and https://example.com/image.jpg as two distinct objects, even if they are identical. Shortening the expiration time would decrease, not increase, the cache hit ratio because objects would be re-fetched more frequently. There is no standard HTTP(S) header called "Cache-Region" used for Cloud CDN. Replicating content in Cloud Storage and pointing Cloud CDN to a load balancer on that bucket is a valid architecture for serving static content, but it's a different approach to hosting and doesn't directly address improving the cache hit ratio for an existing Compute Engine setup by optimizing cache keys.