Google PCA Ensure solution and operations reliability Practice Question
This PCA practice question tests your understanding of ensure solution and operations reliability. 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 company runs a critical application on Compute Engine instances in a managed instance group (MIG) with autoscaling. Users report intermittent 503 errors during traffic spikes. Which action should the company take to improve reliability?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure a health check with a sufficient initial delay (grace period) in the MIG
Intermittent 503 errors during traffic spikes often indicate that new VM instances are being started but are not yet ready to serve traffic, causing the load balancer to forward requests to them prematurely. Configuring a health check with a sufficient initial delay (grace period) in the MIG ensures that newly created instances are given time to fully initialize and pass health checks before they receive traffic, preventing 503 errors. This directly addresses the root cause by allowing the application to become healthy before being added to the load balancer's backend.
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.
✗
Change the load balancer from regional to global
Why it's wrong here
Incorrect: global LB does not solve instance readiness issue.
✓
Configure a health check with a sufficient initial delay (grace period) in the MIG
Why this is correct
Correct: ensures instances are healthy before traffic is sent.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the autoscaling cool-down period from 60s to 120s
Why it's wrong here
Incorrect: longer cool-down delays scaling, not helps readiness.
✗
Increase the maximum number of instances in the MIG
Why it's wrong here
Incorrect: adds capacity but does not prevent 503 during scale-up.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that scaling-related errors are always solved by increasing capacity or adjusting scaling parameters, when in fact the root cause is often a misconfigured health check or insufficient initialization time for new instances.
Detailed technical explanation
How to think about this question
The health check grace period (initial delay) in a MIG is defined by the `initial_delay_sec` parameter, which defaults to 300 seconds but can be tuned based on application startup time. During this period, the instance is excluded from the load balancer's backend service, preventing 503 errors from premature traffic. Under the hood, the load balancer uses HTTP health checks (e.g., HTTP 200 on a specific path) to determine instance readiness, and without a sufficient grace period, instances may fail health checks and be repeatedly recreated, causing a crash loop.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this PCA question in full detail.
Ensure solution and operations reliability — This question tests Ensure solution and operations reliability — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure a health check with a sufficient initial delay (grace period) in the MIG — Intermittent 503 errors during traffic spikes often indicate that new VM instances are being started but are not yet ready to serve traffic, causing the load balancer to forward requests to them prematurely. Configuring a health check with a sufficient initial delay (grace period) in the MIG ensures that newly created instances are given time to fully initialize and pass health checks before they receive traffic, preventing 503 errors. This directly addresses the root cause by allowing the application to become healthy before being added to the load balancer's backend.
What should I do if I get this PCA 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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Question Discussion
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