Quick Answer
The answer is to roll back the most recent deployment. When the error budget is exhausted, the immediate priority is to stop further degradation by restoring the service to a known stable state, which the HTTP(S) load balancer will automatically serve once the rollback completes. This follows the core incident management principle of “mitigate first, investigate later”—reducing user impact takes precedence over root cause analysis. On the Google Professional Cloud DevOps Engineer exam, this scenario tests your understanding of SRE practices and the error budget policy as a deployment safety valve. A common trap is to start debugging or scaling up resources, but the correct reflex is always to roll back first, because every moment spent investigating consumes more of an already depleted budget. Memory tip: when the budget is bust, roll back or you’ll be dust.
This PCDOE practice question tests your understanding of managing service incidents. 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 DevOps engineer receives an alert that the error budget for a critical service has been exhausted. The service runs on Compute Engine behind an HTTP(S) load balancer. The team wants to reduce the impact on users while investigating. What should the engineer do first?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Roll back the most recent deployment
Rolling back quickly restores the previous stable version.
Begin a detailed postmortem analysis
Why wrong: Postmortem should happen after mitigation, not before.
Disable the alerting policy to reduce noise
Why wrong: Ignoring alerts does not resolve the incident.
Increase the number of instances in the managed instance group
Why wrong: Scaling out may not address the root cause and could increase costs.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Roll back the most recent deployment
Rolling back the most recent deployment is the correct first action because it immediately restores the service to a known stable state, stopping further consumption of the error budget. This aligns with the incident management principle of 'mitigate first, investigate later' — reducing user impact takes priority over root cause analysis. The HTTP(S) load balancer will automatically route traffic to the previous healthy version once the rollback is complete.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Roll back the most recent deployment
Why this is correct
Rolling back quickly restores the previous stable version.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Begin a detailed postmortem analysis
Why it's wrong here
Postmortem should happen after mitigation, not before.
Disable the alerting policy to reduce noise
Why it's wrong here
Ignoring alerts does not resolve the incident.
Increase the number of instances in the managed instance group
Why it's wrong here
Scaling out may not address the root cause and could increase costs.
Common exam traps
Google Cloud often tests the misconception that scaling out (increasing instances) is the correct response to any degradation, but here the error budget exhaustion indicates a functional defect, not a capacity issue, so scaling would not fix the root cause.
Detailed technical explanation
Error budget exhaustion means the service has exceeded its allowable failure rate over the SLO window (e.g., 99.9% uptime over 30 days). Rolling back leverages the load balancer's traffic splitting or version pinning to shift traffic away from the faulty revision. In practice, the engineer would use `gcloud compute instance-groups managed rolling-action start-update` or a deployment pipeline rollback to revert to the previous image or template.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Managing service incidents — study guide chapter
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FAQ
Managing service incidents — This question tests Managing service incidents — Read the scenario before looking for a memorised answer..
The correct answer is: Roll back the most recent deployment — Rolling back the most recent deployment is the correct first action because it immediately restores the service to a known stable state, stopping further consumption of the error budget. This aligns with the incident management principle of 'mitigate first, investigate later' — reducing user impact takes priority over root cause analysis. The HTTP(S) load balancer will automatically route traffic to the previous healthy version once the rollback is complete.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
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