Google ACE Practice Question: Ensuring successful operation of a cloud solution
This ACE practice question tests your understanding of ensuring successful operation of a cloud solution. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 has deployed a Cloud Run service but receives a 503 error when accessing it. The service logs show 'The request was aborted because there was no available instance.' What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The service is experiencing a spike in traffic and the max instances are too low.
The 503 error with the message 'The request was aborted because there was no available instance' indicates that all current instances are saturated and Cloud Run cannot scale up quickly enough to handle the incoming requests. This occurs when traffic spikes exceed the configured maximum number of instances, causing new requests to be rejected until an instance becomes free. Option C correctly identifies that the max instances setting is too low for the traffic spike.
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.
✗
The minimum number of instances is set too high.
Why it's wrong here
High min instances would keep instances running, reducing the chance of this error.
✗
The container health checks are failing.
Why it's wrong here
Health check failures would result in instances being marked unhealthy, not a lack of instances.
✓
The service is experiencing a spike in traffic and the max instances are too low.
Why this is correct
When all instances are busy, new requests are rejected with a 503 and this log message.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The service's memory limit is set too low.
Why it's wrong here
Low memory might cause OOM, not a 'no available instance' error.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the distinction between scaling limits (max instances) and resource constraints (memory/CPU), where candidates mistakenly attribute 503 errors to resource limits rather than the explicit scaling cap.
Detailed technical explanation
How to think about this question
Cloud Run uses a request-based autoscaling model where the number of instances is dynamically adjusted between the configured min and max instances. When traffic spikes exceed the max instances limit, new requests are queued and eventually rejected with a 503 if no instance becomes available within the request timeout (default 5 minutes). The 'no available instance' error specifically occurs when the concurrency limit per instance (default 80 concurrent requests) is reached across all max instances, and the autoscaler cannot create new instances because the max cap is hit.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this ACE question in full detail.
Ensuring successful operation of a cloud solution — This question tests Ensuring successful operation of a cloud solution — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The service is experiencing a spike in traffic and the max instances are too low. — The 503 error with the message 'The request was aborted because there was no available instance' indicates that all current instances are saturated and Cloud Run cannot scale up quickly enough to handle the incoming requests. This occurs when traffic spikes exceed the configured maximum number of instances, causing new requests to be rejected until an instance becomes free. Option C correctly identifies that the max instances setting is too low for the traffic spike.
What should I do if I get this ACE 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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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