The answer is to set `min_replica_count=1`, which keeps at least one replica always warm and directly eliminates cold start latency for most traffic. This works because Vertex AI’s autoscaling, when `min_replica_count=0`, spins down all replicas to save cost, but a large 5 GB custom container then requires a full cold start—pulling the image, initializing dependencies, and loading the model—before serving the first request. On the Google Professional Machine Learning Engineer exam, this scenario tests your understanding of the trade-off between cost and latency in real-time inference, where the common trap is assuming that optimizing the container image or storage alone (like prebuilding images or using SSDs) can remove the startup overhead. The key insight is that cold start latency is a scaling policy problem, not a container optimization problem. Memory tip: “One warm pod beats any cold start trick”—always think of `min_replica_count` as the first lever to pull when latency spikes from idle scaling.
PMLE Serving and scaling models Practice Question
This PMLE practice question tests your understanding of serving and scaling models. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 team deploys a real-time model using a custom container on Vertex AI Prediction. The container is large (5 GB) and cold starts are causing latency spikes. The endpoint is configured with `min_replica_count=0` to reduce cost. The team wants to keep the cost low while reducing cold starts. What is the best approach?
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
✓
Set `min_replica_count=1` to keep at least one replica always warm.
Option B is correct because configuring a minimum number of always-on replicas (e.g., 1) eliminates cold starts for most traffic. Option A is wrong because it may not help if container is large. Option C is wrong because prebuilding images doesn't reduce cold start startup overhead. Option D is wrong because SSD can help but not eliminate cold start latency.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Set `min_replica_count=1` to keep at least one replica always warm.
Why this is correct
A single warm replica handles traffic immediately while autoscaling adds more.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
Use a prebuilt container for the model framework to reduce image size.
Why it's wrong here
Custom container is already needed; prebuilt may not have custom dependencies.
✗
Enable container memory optimization to reduce startup time.
Why it's wrong here
Startup time is dominated by container image download and model loading, not memory optimization.
✗
Provision a Persistent Disk (SSD) for the container image to speed up download.
Why it's wrong here
Persistent disk is not used for container image caching; image is stored in Container Registry and pulled each time.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PMLE NAT questions on configuration and troubleshooting.
Serving and scaling models — This question tests Serving and scaling models — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Set `min_replica_count=1` to keep at least one replica always warm. — Option B is correct because configuring a minimum number of always-on replicas (e.g., 1) eliminates cold starts for most traffic. Option A is wrong because it may not help if container is large. Option C is wrong because prebuilding images doesn't reduce cold start startup overhead. Option D is wrong because SSD can help but not eliminate cold start latency.
What should I do if I get this PMLE question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PMLE NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This PMLE 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 PMLE exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.