Google ACE Deploying and Implementing a Cloud Solution Practice Question

A team is creating a managed instance group (MIG) for a stateless web application. They need to ensure that instances are automatically replaced if they become unhealthy and that new instances are rolled out gradually with no downtime during updates. Which set of configurations should they use?

⚠ Common exam trap

ACE often tests the pairing of health checks with autohealing and the maxSurge/maxUnavailable semantics, trapping candidates who assume any rolling update configuration provides zero downtime.

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

✓

Create a MIG with a health check configured for autohealing; set rolling update with maxSurge=1 and maxUnavailable=0.

A health check is required for autohealing — without it, the MIG cannot detect unhealthy instances and replace them. For zero-downtime rolling updates, maxSurge=1 allows a new instance to be created before an old one is removed, while maxUnavailable=0 guarantees the desired capacity is never reduced during the update. This combination satisfies both requirements.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
Create a MIG without health check; set rolling update with maxSurge=1 and maxUnavailable=0.
Why it's wrong here
Omitting the health check means the MIG never marks instances unhealthy, so autohealing cannot replace them. It is tempting because maxSurge=1 with maxUnavailable=0 does add new instances before removing old ones, which would be correct for zero-downtime updates if autohealing were not also required.
✗
Create a MIG with a health check for autohealing; set rolling update with maxSurge=0 and maxUnavailable=1.
Why it's wrong here
maxSurge=0 with maxUnavailable=1 terminates an instance before its replacement is ready, so serving capacity drops and downtime occurs during updates. It is tempting because the health check does enable autohealing, and this setting would be correct where capacity is over-provisioned and brief unavailability is tolerable.
✓
Create a MIG with a health check configured for autohealing; set rolling update with maxSurge=1 and maxUnavailable=0.
Why this is correct
The health check drives autohealing, replacing unhealthy instances automatically. maxSurge=1 with maxUnavailable=0 keeps capacity at or above target throughout the rolling update, so no instance is removed before a replacement is ready, satisfying the no-downtime constraint.
✗
Create a MIG without health check; set rolling update with maxSurge=0 and maxUnavailable=1.
Why it's wrong here
Without a health check the MIG cannot detect unhealthy instances, so autohealing never triggers; maxSurge=0 and maxUnavailable=1 also removes capacity during updates. It is tempting because maxUnavailable=1 does roll out instances gradually, and this configuration would suit a non-critical workload where brief downtime is acceptable.

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Google ACE Deploying and Implementing a Cloud Solution Practice Question

Why each option matters

Option-by-option breakdown

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