The answer is blue/green deployment with health checks and a managed instance group. This strategy minimizes downtime by launching the new green version in a separate managed instance group, where it undergoes health checks before any traffic is shifted from the old blue group. If the green VMs fail those checks, the managed instance group automatically keeps the blue version serving, providing zero downtime and an instant rollback without manual intervention. On the Google Professional Cloud Developer exam, this scenario tests your understanding of how to combine instance group health checks with traffic splitting for safe, automated releases. A common trap is choosing a rolling update, which can still cause partial downtime or require manual rollback steps. Remember the key distinction: blue/green keeps both environments fully live until the new one is verified, while rolling updates replace instances incrementally. Memory tip: “Blue stays true until green is clean” — the old version keeps serving until the new one passes all health checks.
PCD Deploying applications Practice Question
This PCD practice question tests your understanding of deploying applications. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 DevOps engineer is automating deployments to Compute Engine using a CI/CD pipeline. They want to minimize downtime and ensure that if a new VM fails health checks, the old VM continues serving. Which 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
✓
Blue/green deployment with health checks and a managed instance group
Blue/green deployment with health checks and a managed instance group is correct because it allows the new version (green) to be fully deployed and validated against health checks before any traffic is switched from the old version (blue). If the new VM fails health checks, the managed instance group automatically keeps the old version serving, ensuring zero downtime and immediate rollback without manual intervention.
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.
✗
Redeploy the old version manually if the new version fails
Why it's wrong here
Manual rollback increases downtime and is error-prone.
✗
Rolling update with a readiness probe
Why it's wrong here
Rolling updates replace instances gradually; if the new version fails, rollback may be slower.
✓
Blue/green deployment with health checks and a managed instance group
Why this is correct
Blue/green allows keeping the old version (blue) serving while the new version (green) is tested; if health checks fail, traffic remains on blue.
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.
✗
Canary deployment with a small percentage of traffic
Why it's wrong here
Canary is safer but does not fully switch traffic until proven; blue/green is more appropriate for full cutover with health checks.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between deployment strategies by making candidates confuse 'rolling update with readiness probe' (which still risks partial downtime during rollback) with 'blue/green deployment' (which isolates the new version entirely until health checks pass).
Detailed technical explanation
How to think about this question
In Google Cloud, a blue/green deployment uses two separate managed instance groups (MIGs) behind a load balancer; health checks are configured at the MIG level using HTTP/S or TCP probes with configurable thresholds (e.g., 2 consecutive failures for unhealthy). The load balancer's backend service can switch traffic atomically by updating the weight of the backend, ensuring zero-downtime cutover. A real-world scenario is deploying a critical payment service where even a single failed health check must block traffic to prevent financial loss.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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: Blue/green deployment with health checks and a managed instance group — Blue/green deployment with health checks and a managed instance group is correct because it allows the new version (green) to be fully deployed and validated against health checks before any traffic is switched from the old version (blue). If the new VM fails health checks, the managed instance group automatically keeps the old version serving, ensuring zero downtime and immediate rollback without manual intervention.
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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