Cloud CDN

Cloud CDN (Content Delivery Network) accelerates content delivery by caching your content at Google's globally distributed edge points of presence (PoPs). It works seamlessly with the External HTTP(S) Load Balancer to reduce latency, lower origin load, and improve user experience for web applications and APIs.

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What Is Cloud CDN?

Cloud CDN is a globally distributed caching layer that sits in front of your backends. When a user requests content, Cloud CDN checks if a cached copy exists at the nearest edge PoP. If it does (a cache hit), the content is served directly from the edge — no round trip to your origin. If not (a cache miss), the request is forwarded to your backend, and the response is cached for future requests.

Key benefits:

• Lower latency — content is served from edge locations close to users.
• Reduced origin load — fewer requests reach your backend servers.
• Lower egress costs — Cloud CDN cache fills and cache-to-client egress are cheaper than standard egress.
• Integrated — Cloud CDN is a checkbox on your External HTTP(S) Load Balancer; no separate infrastructure required.

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How Cloud CDN Works

Request Flow

1. User sends an HTTP(S) request to the load balancer's global anycast IP.
2. Google's edge network routes the request to the nearest PoP.
3. If the response is cached at the PoP, Cloud CDN serves it directly (cache hit).
4. If not cached, the request goes to the backend via the load balancer (cache miss). The response is cached at the edge for subsequent requests.

Cache Keys

The cache key determines what constitutes a unique cacheable object. By default, the cache key includes:

• The URI (scheme, host, path, and query string).

You can customise cache keys to include or exclude:

• Query string parameters (all, none, or specific keys)
• HTTP headers
• Named cookies

This is useful for serving different cached content to different user segments.

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Enabling Cloud CDN

Cloud CDN is enabled per backend service on an External HTTP(S) Load Balancer:

gcloud compute backend-services update my-backend-service \
  --enable-cdn \
  --global

For backend buckets (Cloud Storage serving static assets):

gcloud compute backend-buckets update my-bucket-backend \
  --enable-cdn

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Cache Modes

Cloud CDN offers three cache modes: