The answer is to use a wildcard in the Cloud CDN invalidation path, such as `/images/*`. This is correct because Cloud CDN cache invalidation requires exact path matching by default; invalidating a specific path like `/images/` only clears the cached object for that exact directory key, not the individual image files stored under it. A wildcard ensures all objects beneath the directory are invalidated, forcing the CDN to fetch the updated assets from the backend. On the Google Professional Cloud Developer exam, this tests your understanding of how Cloud CDN’s invalidation API treats paths literally, a common trap where candidates assume directory-level invalidation cascades to subpaths. Remember the memory tip: “Wildcards wipe out the whole directory; exact paths only hit the front door.”
PCD Building and testing applications Practice Question
This PCD practice question tests your understanding of building and testing applications. 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 company serves static content (images, CSS) through a Cloud Load Balancer with Cloud CDN enabled. They release a new version of the website with updated image assets. After deployment, users still see old images, even though the new image files are served from the backend. The team has already invalidated the cache for the directory containing the images using the Cloud CDN invalidation feature with a specific path. However, the old images persist. What is the most effective additional step to ensure users see the new images?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a wildcard in the Cloud CDN invalidation path (e.g., /images/*).
Option B is correct because Cloud CDN cache invalidation requires exact path matching unless a wildcard is used. The team invalidated a specific path but likely missed the exact paths of the cached image files. Using a wildcard like `/images/*` ensures all objects under the `/images/` directory are invalidated, forcing the CDN to fetch the updated images from the backend.
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.
✗
Set the cache TTL for the image directory to 0 seconds.
Why it's wrong here
Setting TTL to 0 effectively disables caching for new objects but does not clear existing cache entries.
✓
Use a wildcard in the Cloud CDN invalidation path (e.g., /images/*).
Why this is correct
A wildcard ensures all objects under /images/ are invalidated, even if URLs have query parameters or other variations.
Related concept
Read the scenario before looking for a memorised answer.
✗
Change the load balancer cache mode to 'FORCE_CACHE_ALL'.
Why it's wrong here
This mode caches all responses but does not invalidate existing cache entries.
✗
Configure cache key parameters to ignore query strings.
Why it's wrong here
This affects how objects are cached but does not force re-fetching of already cached objects.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the nuance that Cloud CDN invalidation requires exact paths or wildcards, and candidates mistakenly think that invalidating a directory path (without a wildcard) will clear all files within it.
Detailed technical explanation
How to think about this question
Cloud CDN invalidation uses exact path matching by default, meaning a request to invalidate `/images/logo.png` only removes that specific object. Wildcards (`*`) match any number of characters, so `/images/*` invalidates all objects under the `/images/` prefix. Invalidation is asynchronous and can take up to 5 minutes to propagate across all edge caches, but it is the only way to immediately purge cached content without waiting for TTL expiry.
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.
Building and testing applications — This question tests Building and testing applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a wildcard in the Cloud CDN invalidation path (e.g., /images/*). — Option B is correct because Cloud CDN cache invalidation requires exact path matching unless a wildcard is used. The team invalidated a specific path but likely missed the exact paths of the cached image files. Using a wildcard like `/images/*` ensures all objects under the `/images/` directory are invalidated, forcing the CDN to fetch the updated images from the backend.
What should I do if I get this PCD question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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 PCD 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 PCD 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.