The answer is that the invalidation path does not match the full cache key because signed URLs include query parameters. Cloud CDN constructs its cache key from the entire URL, including the query string parameters like `?Expires=...&Signature=...` used for signed URL authentication. When you run the invalidation command with only the path `/videos/incident.mp4`, it fails to match the cached entry that includes those query parameters, so the old content remains served despite a successful invalidation response. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding of how cache key composition interacts with invalidation—a common trap is assuming the path alone is sufficient. Remember that for cloud CDN cache invalidation with signed URLs, you must either invalidate with the exact query string or use a wildcard pattern that covers the full cache key. A useful memory tip: "Sign the URL, sign the invalidation—match the full key to purge the cache."
PCNE Configuring network services Practice Question
This PCNE practice question tests your understanding of configuring network services. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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.
Option C is correct because 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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The Cloud Storage bucket requires object versioning to be enabled for invalidation.
Why it's wrong here
Object versioning is not required.
Common exam traps
Common exam trap: answer the scenario, not the keyword
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.
Detailed technical explanation
How to think about this question
Cloud CDN constructs the cache key from the URL, including the path and, by default, all query parameters. When signed URLs are used, the query parameters (e.g., `Expires`, `Signature`, `KeyName`) become part of the cache key, making each signed URL a unique cache entry. The `gcloud compute url-maps invalidate-cdn-cache` command invalidates entries whose cache key matches the given path prefix or exact path, but it does not automatically strip query parameters. Therefore, to invalidate a specific signed URL, you must include the exact query string in the `--path` argument, or use a wildcard pattern if supported.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Configuring network services — This question tests Configuring network services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The invalidation path does not match the cache key because signed URLs include query parameters. — Option C is correct because 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.
What should I do if I get this PCNE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.