- A
Create a separate Cloud Function that receives the file, validates it, and uploads it to Cloud Storage. Invoke the Cloud Function from the client.
Why wrong: Incorrect; adds another component and increases latency and cost.
- B
Have the client send the file to the Cloud Run service, validate the file on the server side, and then upload it to Cloud Storage using the Google Cloud Storage client library.
Correct; validates before upload, keeps architecture simple.
- C
Validate the file on the client side before uploading directly to Cloud Storage, and rely on client-side validation.
Why wrong: Incorrect; client-side validation can be bypassed.
- D
Upload the file to Cloud Storage, then trigger a Cloud Function using Cloud Storage events to validate the file and delete it if invalid.
Why wrong: Incorrect; this approach stores invalid files temporarily and incurs additional cost.
Quick Answer
The answer is to have the client send the file to the Cloud Run service, validate it server-side, and then upload it to Cloud Storage using the client library. This approach is correct because server-side file validation before Cloud Storage upload must inspect both the MIME type and the file’s magic bytes to prevent spoofed extensions, and Cloud Run’s stateless HTTP handler is the ideal place to perform this check before persisting any data. On the Google Professional Cloud Developer exam, this scenario tests your understanding of the “validate-then-store” pattern versus the common trap of relying on client-side checks or pre-signed URLs, which bypass validation entirely. The key insight is that Cloud Run can receive the full binary payload, validate it in memory, and only then write to Cloud Storage—avoiding the cost and complexity of a separate validation service or Cloud Function. Memory tip: “Validate in the handler, store in the bucket”—if the file never touches Cloud Storage before your code inspects it, you control the gate.
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 team is developing a microservice that needs to store user profile images in Cloud Storage. The service is deployed on Cloud Run and will be invoked by other services via HTTP. The images are uploaded by users and the service must validate that the file is an image (e.g., JPEG, PNG) before storing it. The team wants to minimize costs and operational overhead while ensuring that only valid images are stored. The current implementation uploads the file directly to Cloud Storage from the client, but the team wants to add validation in the service. Which approach should the team take?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"minimum / minimize"Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
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
Have the client send the file to the Cloud Run service, validate the file on the server side, and then upload it to Cloud Storage using the Google Cloud Storage client library.
Option B is correct because it keeps the validation logic within the Cloud Run service, which is already deployed and handling HTTP requests. The service can receive the file via HTTP, validate its MIME type and magic bytes on the server side, and then upload it to Cloud Storage using the Google Cloud Storage client library. This minimizes costs (no additional compute services) and operational overhead (single service to manage), while ensuring only valid images are stored.
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.
- ✗
Create a separate Cloud Function that receives the file, validates it, and uploads it to Cloud Storage. Invoke the Cloud Function from the client.
Why it's wrong here
Incorrect; adds another component and increases latency and cost.
- ✓
Have the client send the file to the Cloud Run service, validate the file on the server side, and then upload it to Cloud Storage using the Google Cloud Storage client library.
Why this is correct
Correct; validates before upload, keeps architecture simple.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Validate the file on the client side before uploading directly to Cloud Storage, and rely on client-side validation.
Why it's wrong here
Incorrect; client-side validation can be bypassed.
- ✗
Upload the file to Cloud Storage, then trigger a Cloud Function using Cloud Storage events to validate the file and delete it if invalid.
Why it's wrong here
Incorrect; this approach stores invalid files temporarily and incurs additional cost.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that client-side validation is sufficient for security, or that adding extra serverless functions is always the best way to add validation, when in fact the simplest and most cost-effective approach is to validate within the existing service.
Detailed technical explanation
How to think about this question
Server-side file validation should check both the Content-Type header and the file's magic bytes (e.g., JPEG starts with 0xFF 0xD8, PNG with 0x89 0x50 0x4E 0x47) to prevent MIME type spoofing. Cloud Run can use the `google-cloud-storage` Python or Node.js client library to stream the validated file directly to Cloud Storage, avoiding intermediate storage. This approach also allows the service to enforce size limits and other business rules before the file reaches Cloud Storage.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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.
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FAQ
Questions learners often ask
What does this PCD question test?
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: Have the client send the file to the Cloud Run service, validate the file on the server side, and then upload it to Cloud Storage using the Google Cloud Storage client library. — Option B is correct because it keeps the validation logic within the Cloud Run service, which is already deployed and handling HTTP requests. The service can receive the file via HTTP, validate its MIME type and magic bytes on the server side, and then upload it to Cloud Storage using the Google Cloud Storage client library. This minimizes costs (no additional compute services) and operational overhead (single service to manage), while ensuring only valid images are stored.
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.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 11, 2026
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.
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