PCD Deploying applications Practice Question
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?
⚠ Common exam trap
The PCD exam 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).
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
✓
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.
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.
- ✗
Canary deployment with a small percentage of traffic
Why it's wrong here
Canary deployment is unsuitable here because it routes a small percentage of live traffic to the new, potentially failing VM, meaning some users would experience downtime if health checks fail. The requirement is for the old VM to continue serving *without impact* if the new VM is unhealthy. This strategy is tempting as it facilitates a controlled, gradual rollout, allowing for real-world validation of new versions with minimal *overall* blast radius. It is ideal for testing new features or performance in production with a subset of users before a full release.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCD 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 PCD exam.