- A
Use the 'gcloud run deploy' command with '--no-traffic' and then use 'gcloud run services update-traffic --to-revisions=REVISION=5' to send 5% of traffic.
This directly sets a specific percentage of traffic to the new revision.
- B
Use the 'gcloud run deploy' command with '--no-traffic' to deploy without serving traffic, then use 'gcloud run services update-traffic' to gradually increase traffic.
This allows deploying a revision without routing traffic and then incrementally shifting traffic to it.
- C
Set the 'max-instances' parameter to limit the number of instances handling requests.
Why wrong: max-instances controls concurrency, not traffic splitting.
- D
Use the 'gcloud run deploy' command with '--tag' to assign a tag to the new revision, then direct test traffic to that tag.
Why wrong: Tags are used for internal testing without routing production traffic, but they don't support percentage-based traffic splitting.
- E
Deploy the new revision with the same revision name as the old one to overwrite it, then roll back if issues occur.
Why wrong: This does a full replacement, not a canary or gradual rollout.
Quick Answer
The correct approach is to deploy the new revision with the `--no-traffic` flag and then use `gcloud run services update-traffic` to gradually shift a small percentage of traffic to it. This two-step process is the standard canary deployment pattern on Cloud Run because it allows you to validate a new revision in production without immediately impacting all users, using Cloud Run’s built-in traffic splitting capabilities. On the Google Professional Cloud Developer exam, this scenario tests your understanding of Cloud Run’s revision management and traffic routing, often appearing as a multi-select question where one distractor suggests using a single command like `gcloud run deploy --traffic` to split traffic immediately, which is incorrect because that would serve traffic to the new revision right away. A common trap is forgetting that `--no-traffic` must be used first to decouple deployment from traffic assignment. Memory tip: think “Deploy dark, then light the canary” — deploy with no traffic first, then use update-traffic to send a small percentage.
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 developer is deploying a new version of a microservice to Cloud Run. The developer wants to ensure that the new revision is tested with a small percentage of traffic before rolling out to all users. Which TWO approaches can the developer use?
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
Use the 'gcloud run deploy' command with '--no-traffic' and then use 'gcloud run services update-traffic --to-revisions=REVISION=5' to send 5% of traffic.
Option A is correct because the '--no-traffic' flag deploys the new revision without serving any traffic, and then 'gcloud run services update-traffic --to-revisions=REVISION=5' allows you to send exactly 5% of traffic to that revision for canary testing. Option B is also correct because it describes the same two-step process: deploy with '--no-traffic' to avoid immediate traffic, then use 'update-traffic' to gradually increase the percentage, which is the standard canary deployment pattern on Cloud Run.
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.
- ✓
Use the 'gcloud run deploy' command with '--no-traffic' and then use 'gcloud run services update-traffic --to-revisions=REVISION=5' to send 5% of traffic.
Why this is correct
This directly sets a specific percentage of traffic to the new revision.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Use the 'gcloud run deploy' command with '--no-traffic' to deploy without serving traffic, then use 'gcloud run services update-traffic' to gradually increase traffic.
Why this is correct
This allows deploying a revision without routing traffic and then incrementally shifting traffic to it.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Set the 'max-instances' parameter to limit the number of instances handling requests.
Why it's wrong here
max-instances controls concurrency, not traffic splitting.
- ✗
Use the 'gcloud run deploy' command with '--tag' to assign a tag to the new revision, then direct test traffic to that tag.
Why it's wrong here
Tags are used for internal testing without routing production traffic, but they don't support percentage-based traffic splitting.
- ✗
Deploy the new revision with the same revision name as the old one to overwrite it, then roll back if issues occur.
Why it's wrong here
This does a full replacement, not a canary or gradual rollout.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the distinction between traffic splitting (percentage-based routing) and direct access via tags; candidates mistakenly think tagging alone can serve a percentage of production traffic, but tags only provide a separate URL for testing without affecting the main service's traffic distribution.
Detailed technical explanation
How to think about this question
Cloud Run uses a traffic routing model based on revision-level percentages, managed via the 'spec.traffic' field in the Service YAML. The 'gcloud run services update-traffic' command modifies this field to set a percentage for each revision, and the sum must equal 100. Under the hood, Cloud Run's load balancer uses these percentages to distribute incoming requests, enabling canary deployments without downtime. A real-world scenario is when you want to test a new revision with 5% of live traffic for 10 minutes, then ramp to 100% if no errors occur.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
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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: Use the 'gcloud run deploy' command with '--no-traffic' and then use 'gcloud run services update-traffic --to-revisions=REVISION=5' to send 5% of traffic. — Option A is correct because the '--no-traffic' flag deploys the new revision without serving any traffic, and then 'gcloud run services update-traffic --to-revisions=REVISION=5' allows you to send exactly 5% of traffic to that revision for canary testing. Option B is also correct because it describes the same two-step process: deploy with '--no-traffic' to avoid immediate traffic, then use 'update-traffic' to gradually increase the percentage, which is the standard canary deployment pattern on Cloud Run.
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.
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Last reviewed: Jun 30, 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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