How to Resolve Cloud CDN Caching Conflicts with Private Headers?
You want Cloud CDN to serve the https://www.example.com/images/spacetime.png static image file that is hosted in a private Cloud Storage bucket. You are using the USE_ORIGIN_HEADERS cache mode. You receive an HTTP 403 error when opening the file in your browser, and you see that the HTTP response has a Cache-Control: private, max-age=0 header. How should you correct this issue?
Community Votes
67% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
Tests the interaction between Cloud CDN cache modes and origin Cache-Control headers, with the common trap being the misinterpretation of a 403 response as an IAM permission failure rather than a caching policy block.
This scenario examines how Google Cloud CDN processes restrictive origin cache directives like Cache-Control: private. Community analysis confirms that switching to Force cache all content overrides these restrictions, enabling successful delivery of private bucket assets.
Option A is frequently selected because candidates link the HTTP 403 status to error handling, but negative caching only stores failed responses and does not resolve the underlying Cache-Control conflict preventing the object from being cached.
Community Discussion (5 comments)
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Expert Analysis
Why the Answer Is Correct
Under the USE_ORIGIN_HEADERS cache mode, Cloud CDN strictly adheres to the origin's Cache-Control directives. When the backend returns Cache-Control: private, max-age=0, the CDN treats the object as uncacheable and blocks public distribution. Switching to FORCE_CACHE_ALL instructs Cloud CDN to ignore restrictive origin headers, allowing it to cache and serve the private image file globally without violating the origin's caching policy intent for end users.Why the Other Options Are Wrong
Enabling negative caching (Option A) only stores and serves HTTP error responses when backends fail; it does not override Cache-Control directives on content that is simply marked as private. Option C is invalid because Cloud CDN lacks a generic backend TTL parameter to bypass private headers, and adjusting TTL would not change the fundamental caching behavior dictated by the origin. The reported 403 actually stems from the CDN refusing to cache or distribute the asset due to the restrictive header, not actual storage permissions.Community Comment Notes
Comment [3] accurately explains that FORCE_CACHE_ALL bypasses restrictive headers like Cache-Control: private, directly addressing the core mechanism tested. Comments [1], [2], and [4] incorrectly attribute the 403 to missing IAM permissions or backend service settings, overlooking the explicit Cache-Control header provided in the prompt. Comment [1] also helpfully points out that negative caching is specifically designed for other error codes, reinforcing why it is not the primary solution here.Official Reference
Exam Strategy
Always verify whether a reported HTTP error stems from identity/access controls or caching policy conflicts before selecting permission-related fixes. For Cloud CDN questions involving Cache-Control headers, prioritize cache mode selection over TTL adjustments, as modes dictate how directives are processed at the edge.
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