The answer is to create two Deployments (stable and canary) with different numbers of replicas and use the same Service label. This is correct because on GKE, a canary deployment for gradual traffic shifting relies on a single Service distributing traffic proportionally based on the replica count of each Deployment sharing its selector label. By adjusting the number of canary replicas, you control the percentage of traffic shifted to the new version, minimizing risk while validating the update. On the Google Professional Cloud Developer exam, this scenario tests your understanding of native Kubernetes traffic routing without advanced tools like Istio or GKE Gateway—a common trap is assuming a single Deployment with a rolling update suffices, but that lacks fine-grained canary control. Remember the memory tip: “Same Service, separate Deployments—replicas drive the ratio.”
PCD Deploying applications Practice Question
This PCD practice question tests your understanding of deploying 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 deploying a critical microservice on GKE. They want to minimize risk by gradually shifting traffic from old to new version. They use a Deployment with a single Service. What deployment strategy should they implement?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create two Deployments (stable and canary) with different numbers of replicas and use the same Service label.
Option D is correct because it implements a canary deployment pattern on GKE: two separate Deployments (stable and canary) share the same Service label, allowing the Service to distribute traffic to both based on replica counts. This enables gradual traffic shifting by adjusting the number of canary replicas, minimizing risk while the new version is validated.
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 a rolling update with maxSurge=1 and maxUnavailable=0.
Why it's wrong here
Rolling update updates pods gradually but does not allow fine-grained traffic splitting.
✗
Use a single Deployment with a readinessProbe that fails for the new version until ready.
Why it's wrong here
Readiness probe does not control traffic percentage.
✗
Create two separate Deployments and switch the Service selector to the new version after testing.
Why it's wrong here
This is blue/green, but switching selector immediately shifts all traffic.
✓
Create two Deployments (stable and canary) with different numbers of replicas and use the same Service label.
Why this is correct
Canary with multiple Deployments allows traffic splitting based on replica count.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between a rolling update (which is automatic and immediate) and a canary deployment (which requires manual or tool-driven replica scaling to control traffic percentage), leading candidates to mistakenly choose a rolling update option when gradual traffic shifting is explicitly required.
Detailed technical explanation
How to think about this question
In GKE, a canary deployment leverages the fact that a Service's label selector matches pods from multiple Deployments as long as they share the same label key-value pair. By adjusting the replica count of the canary Deployment (e.g., 1 canary vs. 9 stable), you achieve a 10% traffic split via kube-proxy's round-robin load balancing. This approach also allows easy rollback by scaling the canary to zero, without modifying the Service selector.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Deploying applications — This question tests Deploying applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create two Deployments (stable and canary) with different numbers of replicas and use the same Service label. — Option D is correct because it implements a canary deployment pattern on GKE: two separate Deployments (stable and canary) share the same Service label, allowing the Service to distribute traffic to both based on replica counts. This enables gradual traffic shifting by adjusting the number of canary replicas, minimizing risk while the new version is validated.
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.
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Question Discussion
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