The answer is setting a minimum number of instances. This configuration directly addresses Cloud Run cold start reduction by ensuring that at least one container instance remains warm and idle, ready to handle incoming requests without the latency of initializing a new instance. On the Google Professional Cloud Developer exam, this question tests your understanding of how to balance performance and cost; the key insight is that idle minimum instances are billed at a lower rate than active instances, making this the most cost-effective solution compared to increasing CPU or memory, which would raise per-request costs. A common trap is choosing always-on CPU, which keeps the instance active but incurs full compute charges even when idle, whereas minimum instances only charge a reduced idle rate. Remember the memory tip: “Keep one warm, pay less per storm” — a single warm instance eliminates the cold-start storm without burning your budget.
PCD Practice Question: Designing highly scalable, available, and reliable cloud-native applications
This PCD practice question tests your understanding of designing highly scalable, available, and reliable cloud-native 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.
An application running on Cloud Run experiences cold starts causing latency spikes. What is the most cost-effective solution to reduce cold starts?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set a minimum number of instances
Setting a minimum number of instances ensures that Cloud Run always keeps at least one instance warm (idle) to serve incoming requests instantly, eliminating cold start latency. This is the most cost-effective solution because you only pay for the minimum instances when they are idle (at a reduced rate), whereas other options increase per-request cost or do not address the root cause of cold starts.
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.
✓
Set a minimum number of instances
Why this is correct
Minimum instances keep the specified number of instances always warm, eliminating cold starts for those instances.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the container's CPU allocation
Why it's wrong here
Increasing CPU does not address cold starts; it may increase cost without reducing latency.
✗
Enable HTTP keep-alive connections
Why it's wrong here
HTTP keep-alive helps with connection reuse but does not prevent cold starts.
✗
Use a larger container memory size
Why it's wrong here
Larger memory does not prevent cold starts; it may increase cost.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that scaling resources (CPU or memory) or optimizing network connections can eliminate cold starts, but the only way to prevent cold starts is to keep instances warm, which is achieved by setting a minimum number of instances.
Detailed technical explanation
How to think about this question
Cloud Run's minimum instances feature uses the 'min-instance' annotation (specified via --min-instances flag) to pre-warm instances, which are billed at a reduced idle rate (approximately 10% of the active rate) while waiting for traffic. Under the hood, Cloud Run keeps the container's runtime environment ready, including loaded dependencies and cached data, so that the first request bypasses the cold start sequence (container startup, entrypoint execution, and health check). In real-world scenarios, this is critical for applications with unpredictable traffic patterns, such as webhook handlers or APIs with sporadic bursts, where even a 1-2 second cold start can cause timeouts or poor user experience.
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 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Designing highly scalable, available, and reliable cloud-native applications — This question tests Designing highly scalable, available, and reliable cloud-native applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Set a minimum number of instances — Setting a minimum number of instances ensures that Cloud Run always keeps at least one instance warm (idle) to serve incoming requests instantly, eliminating cold start latency. This is the most cost-effective solution because you only pay for the minimum instances when they are idle (at a reduced rate), whereas other options increase per-request cost or do not address the root cause of cold starts.
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.
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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