PCNE Configuring Network Services Practice Question
A media streaming company uses Cloud CDN with signed URLs to protect content. They want to invalidate cached content for a specific file after a security incident. The file is stored in a Cloud Storage bucket and the CDN cache key includes the URL. They run: gcloud compute url-maps invalidate-cdn-cache URL_MAP --path "/videos/incident.mp4". The invalidation succeeds but the old content is still served. What is the most likely reason?
⚠ Common exam trap
Google Cloud often tests the misconception that cache invalidation by path alone will work for all cached objects, ignoring that signed URLs or query parameters can create distinct cache entries that require matching the full cache key.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The invalidation path does not match the cache key because signed URLs include query parameters.
Cloud CDN's cache key for signed URLs includes the query parameters (e.g., `?Expires=...&Signature=...`). The invalidation command specifies only the path `/videos/incident.mp4`, which does not match the full cache key that includes the query string. As a result, the invalidation does not purge the cached entry for the signed URL, and the old content continues to be served.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The Cloud CDN cache key does not include query parameters, so the invalidation should work.
Why it's wrong here
But signed URLs add query parameters that become part of the cache key.
- ✗
The Cache-Control header on the object is set to public, max-age=31536000.
Why it's wrong here
CDN invalidation overrides TTL.
- ✓
The invalidation path does not match the cache key because signed URLs include query parameters.
Why this is correct
With signed URLs, each request has unique query strings, so the cache key varies.
- ✗
The Cloud Storage bucket requires object versioning to be enabled for invalidation.
Why it's wrong here
Object versioning is not required.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCNE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCNE exam.