The answer is a rolling update on the managed instance group. This is the correct choice because a rolling update incrementally replaces instances with patched versions, and the TCP load balancer automatically directs traffic only to healthy instances, ensuring zero downtime during the process. On the Google Professional Cloud Developer exam, this scenario tests your understanding of managed instance group update strategies, often appearing as a distractor against blue/green deployments or instance templates. A common trap is choosing a blue/green strategy, which is overkill for simple security patches and introduces additional cost and complexity. Remember the key distinction: rolling updates are ideal for incremental, in-place changes like security patches, while blue/green is better for major version swaps. Memory tip: think "Rolling for patching, Blue/Green for changing."
PCD Deploying applications Practice Question
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.
A developer is deploying an application on Compute Engine and needs to automatically apply security patches without downtime. The application runs behind a TCP load balancer. What is the best deployment strategy?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a rolling update on the instance group.
Option D is correct because a rolling update on a managed instance group allows the developer to update instances incrementally, applying security patches without downtime. The TCPload balancer automatically distributes traffic only to healthy instances, so as each instance is updated and passes health checks, traffic is seamlessly redirected away from instances being patched.
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.
✗
Use a canary deployment with a separate instance group.
Why it's wrong here
Canary is for testing a new version with a small subset, not for patching all instances.
✗
Stop all instances, apply patches, then restart them.
Why it's wrong here
Causes downtime.
✗
Use a managed instance group with autohealing.
Why it's wrong here
Autohealing only recreates instances that fail health checks, not for applying patches.
✓
Use a rolling update on the instance group.
Why this is correct
Rolling update gradually replaces instances with new ones that have patches, minimizing downtime while behind a load balancer.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between reactive mechanisms like autohealing and proactive strategies like rolling updates, leading candidates to mistakenly choose autohealing for patching when it only handles failure recovery, not scheduled maintenance.
Detailed technical explanation
How to think about this question
A rolling update in Compute Engine uses a `maxSurge` and `maxUnavailable` configuration to control the number of instances updated at a time, ensuring capacity is maintained. The TCPload balancer relies on health checks (e.g., TCP health probes on a specific port) to determine instance readiness; during a rolling update, instances are drained of existing connections before being terminated, and new connections are routed to updated instances only after they pass health checks. This approach aligns with Google Cloud's recommended practice for zero-downtime patching, as it leverages the managed instance group's update policies and the load balancer's connection draining feature.
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: Use a rolling update on the instance group. — Option D is correct because a rolling update on a managed instance group allows the developer to update instances incrementally, applying security patches without downtime. The TCP load balancer automatically distributes traffic only to healthy instances, so as each instance is updated and passes health checks, traffic is seamlessly redirected away from instances being patched.
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: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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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