- A
Delete the blue Deployment and create the green Deployment as the replacement
Why wrong: Deleting the blue Deployment first creates downtime between deletion and creation. Blue-green keeps both running simultaneously.
- B
Update the Service's label selector from 'version: blue' to 'version: green'
Changing the Service selector instantly redirects all new traffic to green Pods. Blue Pods continue running for instant rollback — simply change the selector back.
- C
Update the Deployment's container image tag — GKE automatically performs a blue-green rollout
Why wrong: Updating the container image triggers a RollingUpdate by default, not a blue-green switch. Blue-green requires separate Deployments with a Service selector switch.
- D
Use kubectl patch to update the Service's ClusterIP to point to the green Deployment
Why wrong: ClusterIP is assigned by Kubernetes and cannot be manually patched to point to a different Deployment — Services route via label selectors, not IPs.
Quick Answer
The answer is to update the Service's label selector from 'version: blue' to 'version: green'. This works because a Kubernetes Service acts as a stable network abstraction that routes traffic to Pods based on matching labels; by changing the selector, the Service instantly re-routes all incoming requests to the green Pods without any downtime or redeployment. On the Google Associate Cloud Engineer exam, this question tests your understanding of how Services decouple traffic routing from Pod lifecycles, and a common trap is assuming you need to modify the Ingress or recreate the Service. The key insight is that the selector change is instantaneous and reversible—simply switching back to 'version: blue' enables a rollback in seconds. Remember: the Service is the traffic switch, not the deployment.
Google ACE Deploying and implementing a cloud solution Practice Question
This ACE practice question tests your understanding of deploying and implementing a cloud solution. 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 deploys a new version of their application using a blue-green strategy on GKE. The 'green' deployment is running but still in testing. When ready, traffic should instantly switch from 'blue' to 'green' with rollback possible in seconds. How is the instant switch implemented?
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
Update the Service's label selector from 'version: blue' to 'version: green'
Option B is correct because in a blue-green deployment on GKE, the Service acts as a stable network endpoint abstracting the underlying Pods. By changing the Service's label selector from 'version: blue' to 'version: green', traffic is instantly routed to the green Pods without any downtime or need to recreate resources. This allows immediate rollback by simply reverting the selector back to 'version: blue'.
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.
- ✗
Delete the blue Deployment and create the green Deployment as the replacement
Why it's wrong here
Deleting the blue Deployment first creates downtime between deletion and creation. Blue-green keeps both running simultaneously.
- ✓
Update the Service's label selector from 'version: blue' to 'version: green'
Why this is correct
Changing the Service selector instantly redirects all new traffic to green Pods. Blue Pods continue running for instant rollback — simply change the selector back.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Update the Deployment's container image tag — GKE automatically performs a blue-green rollout
Why it's wrong here
Updating the container image triggers a RollingUpdate by default, not a blue-green switch. Blue-green requires separate Deployments with a Service selector switch.
- ✗
Use kubectl patch to update the Service's ClusterIP to point to the green Deployment
Why it's wrong here
ClusterIP is assigned by Kubernetes and cannot be manually patched to point to a different Deployment — Services route via label selectors, not IPs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that updating a Deployment's image tag or using kubectl patch on ClusterIP is the correct way to switch traffic, when in fact the Service's label selector is the precise mechanism for instant traffic redirection in blue-green deployments.
Detailed technical explanation
How to think about this question
Under the hood, a Kubernetes Service uses a label selector to dynamically discover Pod endpoints via the Endpoints or EndpointSlice API. When the selector is updated, the kube-proxy on each node immediately updates iptables or IPVS rules to forward traffic to the new Pods, achieving near-instantaneous traffic switching. In real-world scenarios, this pattern is often combined with readiness probes to ensure green Pods are healthy before the selector change, preventing traffic from being sent to unready instances.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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 and implementing a cloud solution — study guide chapter
Learn the concepts, then practise the questions
- →
Deploying and implementing a cloud solution practice questions
Targeted practice on this topic area only
- →
All ACE questions
500 questions across all exam domains
- →
Google Associate Cloud Engineer study guide
Full concept coverage aligned to exam objectives
- →
ACE practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related ACE practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Setting up a cloud solution environment practice questions
Practise ACE questions linked to Setting up a cloud solution environment.
Planning and configuring a cloud solution practice questions
Practise ACE questions linked to Planning and configuring a cloud solution.
Deploying and implementing a cloud solution practice questions
Practise ACE questions linked to Deploying and implementing a cloud solution.
Ensuring successful operation of a cloud solution practice questions
Practise ACE questions linked to Ensuring successful operation of a cloud solution.
Configuring access and security practice questions
Practise ACE questions linked to Configuring access and security.
ACE fundamentals practice questions
Practise ACE questions linked to ACE fundamentals.
ACE scenario practice questions
Practise ACE questions linked to ACE scenario.
ACE troubleshooting practice questions
Practise ACE questions linked to ACE troubleshooting.
Practice this exam
Start a free ACE practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this ACE question test?
Deploying and implementing a cloud solution — This question tests Deploying and implementing a cloud solution — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Update the Service's label selector from 'version: blue' to 'version: green' — Option B is correct because in a blue-green deployment on GKE, the Service acts as a stable network endpoint abstracting the underlying Pods. By changing the Service's label selector from 'version: blue' to 'version: green', traffic is instantly routed to the green Pods without any downtime or need to recreate resources. This allows immediate rollback by simply reverting the selector back to 'version: blue'.
What should I do if I get this ACE 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 →
Last reviewed: Jun 30, 2026
This ACE 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 ACE 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.