- A
Vertex AI endpoint warm-up time; set min replicas to 2 to always keep a warm instance
Increasing min replicas ensures at least one warm instance is always available, reducing cold start latency.
- B
Model loading time is high; enable health checks to warm the instance
Why wrong: Health checks only confirm readiness; they do not prevent the instance from being idle-scaled down.
- C
Network latency; deploy to a different region
Why wrong: Network latency would affect all requests, not just cold starts.
- D
Container initialization delay; use a smaller container image
Why wrong: Smaller images help but the primary issue is that an instance might be terminated when idle; min replicas=1 does not guarantee a ready instance after idle.
Question 130 of 1,000
hardMultiple ChoiceObjective-mapped
Cold Start Latency on Vertex AI Endpoints
This PMLE practice question tests your understanding of pmle exam topics. 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 machine learning engineer notices that a model served on Vertex AI Endpoints returns predictions that are consistently 20% slower during the first request after idle (cold start). They are using automatic scaling with min replicas=1. What is the most likely cause and best solution?
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.
Clue:
"first"Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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.
Quick Answer
The answer is to set min replicas to 2 to always keep a warm instance. This is correct because even with automatic scaling and min replicas=1, Vertex AI endpoints can recycle the single instance due to idleness or updates, forcing a cold start where the model must reload into memory—causing the observed 20% latency spike on the first request. On the Google Professional Machine Learning Engineer exam, this tests your understanding of Vertex AI’s scaling behavior and the distinction between “min replicas” as a count versus guaranteed warmth; a common trap is assuming one replica is always active, but Vertex AI may shut it down during prolonged idle periods. The key insight is that cold start latency on Vertex AI endpoints is mitigated not by container size or health checks, but by ensuring at least two replicas so one remains warm while the other handles traffic. Memory tip: “One can go cold, two keep the gold.”
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
✓
Vertex AI endpoint warm-up time; set min replicas to 2 to always keep a warm instance
The correct answer is A. With min replicas=1, a single instance is always running, but it may become idle and require a warm-up period to reload the model into memory, causing the first request to be slower. Setting min replicas to 2 ensures at least one instance remains fully warm to handle requests immediately, reducing cold start latency. Option B is incorrect because health checks measure readiness but do not actively warm the instance; they only prevent traffic until the instance is ready, which doesn't address the delay. Option C is incorrect because network latency would affect all requests consistently, not just the first after idle. Option D is incorrect: a smaller container image reduces initial load time but does not prevent the warm-up delay after idle, and the main issue is the model or endpoint warm-up, not container size.
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.
- ✓
Vertex AI endpoint warm-up time; set min replicas to 2 to always keep a warm instance
Why this is correct
Increasing min replicas ensures at least one warm instance is always available, reducing cold start latency.
Clue confirmation
The clue words "best", "first", "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Model loading time is high; enable health checks to warm the instance
Why it's wrong here
Health checks only confirm readiness; they do not prevent the instance from being idle-scaled down.
- ✗
Network latency; deploy to a different region
Why it's wrong here
Network latency would affect all requests, not just cold starts.
- ✗
Container initialization delay; use a smaller container image
Why it's wrong here
Smaller images help but the primary issue is that an instance might be terminated when idle; min replicas=1 does not guarantee a ready instance after idle.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Identify which PMLE exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Questions learners often ask
What does this PMLE question test?
Read the scenario before looking for a memorised answer.
What is the correct answer to this question?
The correct answer is: Vertex AI endpoint warm-up time; set min replicas to 2 to always keep a warm instance — The correct answer is A. With min replicas=1, a single instance is always running, but it may become idle and require a warm-up period to reload the model into memory, causing the first request to be slower. Setting min replicas to 2 ensures at least one instance remains fully warm to handle requests immediately, reducing cold start latency. Option B is incorrect because health checks measure readiness but do not actively warm the instance; they only prevent traffic until the instance is ready, which doesn't address the delay. Option C is incorrect because network latency would affect all requests consistently, not just the first after idle. Option D is incorrect: a smaller container image reduces initial load time but does not prevent the warm-up delay after idle, and the main issue is the model or endpoint warm-up, not container size.
What should I do if I get this PMLE question wrong?
Identify which PMLE exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "best", "first", "most likely". 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.
About these practice questions
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Last reviewed: Jun 24, 2026
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