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Deploying applications →mediumMultiple ChoiceObjective-mapped

GKE Zero-Downtime Deployment — Blue/Green Strategy | Google Professional Cloud Developer Explained

This PCD practice question tests your understanding of deploying applications. 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.

You need to deploy a critical update to a production service on GKE with zero downtime. Which deployment strategy should you use?

Quick Answer

The answer is a blue/green deployment using a Kubernetes Service and label selector. This strategy achieves zero-downtime by spinning up an entirely new set of pods (the “green” environment) alongside the existing “blue” set, then switching the Service’s label selector to route traffic only after all green pods pass readiness probes. On the Google Professional Cloud Developer exam, this scenario tests your understanding that rolling updates can still cause brief partial downtime during pod termination, while blue/green guarantees a clean traffic cutover. A common trap is choosing canary, which is incremental but not a full zero-downtime guarantee—blue/green is the only option that ensures no requests hit a terminating pod. Remember the mnemonic: “Blue stays live until Green is fully alive.”

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 using a Kubernetes Service and label selector

Blue/green deployment creates two identical environments (blue and green) and switches traffic atomically by updating the Kubernetes Service's label selector to point to the new version. This ensures zero downtime because the old version remains fully serving until the new version is verified, and traffic cutover is instantaneous with no overlapping broken requests.

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.

  • ✗

    Recreate strategy

    Why it's wrong here

    Kills all old pods before creating new ones.

  • ✓

    Blue/green deployment using a Kubernetes Service and label selector

    Why this is correct

    Switches traffic after all new pods are healthy.

    Related concept

    Read the scenario before looking for a memorised answer.

  • ✗

    Canary deployment with 10% traffic

    Why it's wrong here

    Does not guarantee zero downtime for all users.

  • ✗

    Rolling update with maxSurge=25%, maxUnavailable=25%

    Why it's wrong here

    May have temporary unavailability.

Common exam traps

Common exam trap: answer the scenario, not the keyword

A common pitfall on the Google PCD exam is assuming that a rolling update with maxUnavailable=0% guarantees zero downtime, but the given parameters (maxUnavailable=25%) allow some pods to be terminated before new ones are ready, risking downtime. Blue/green deployment with a Service label switch provides atomic traffic cutover with no downtime.

Detailed technical explanation

How to think about this question

Under the hood, a blue/green deployment on GKE typically uses a Kubernetes Service with a label selector that initially matches the 'version: blue' label. To switch traffic, you update the selector to 'version: green', and the Service's iptables rules are updated via kube-proxy, which can take a few seconds to propagate across all nodes. For truly zero downtime, you must ensure the new pods pass readiness probes before the selector change, and you may use a preStop hook to gracefully drain connections from the old pods after the switch.

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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.

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.

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FAQ

Questions learners often ask

What does this PCD question test?

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 using a Kubernetes Service and label selector — Blue/green deployment creates two identical environments (blue and green) and switches traffic atomically by updating the Kubernetes Service's label selector to point to the new version. This ensures zero downtime because the old version remains fully serving until the new version is verified, and traffic cutover is instantaneous with no overlapping broken requests.

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.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Last reviewed: Jul 4, 2026

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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.