The answer is Compute Engine managed instance groups and Cloud Run. Both services automatically scale resources based on load, but they do so in fundamentally different ways that reflect the exam’s focus on choosing the right compute model. Cloud Run is a fully managed serverless platform that uses Knative to automatically adjust container instances based on request concurrency and CPU utilization, even scaling to zero when there is no traffic. Managed instance groups, on the other hand, rely on autoscalers that monitor metrics like CPU usage or HTTP load balancing utilization to add or remove VM instances from a group. On the Google Professional Cloud Developer exam, this question tests your ability to distinguish between serverless and infrastructure-based auto-scaling services; a common trap is selecting App Engine or GKE without recognizing that the question specifically asks for services that automatically scale without manual cluster management. Memory tip: think “serverless scales to zero, MIGs scale to a minimum” — Cloud Run handles the orchestration for you, while MIGs give you control over VM-level scaling policies.
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.
A company is designing a scalable web application on Google Cloud. They expect variable traffic and want to automatically scale resources based on load. Which two services can automatically scale? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Cloud Run
Cloud Run is a fully managed serverless compute platform that automatically scales your containerized applications based on incoming traffic, including scaling to zero when there is no traffic. This autoscaling is handled by the Knative serving layer, which adjusts the number of container instances based on request concurrency and CPU utilization.
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.
✗
Compute Engine unmanaged instance group
Why it's wrong here
Unmanaged instance groups do not support autoscaling; you must manually manage the instances.
✓
Cloud Run
Why this is correct
Cloud Run automatically scales container instances from zero to a maximum based on incoming request volume.
Related concept
Read the scenario before looking for a memorised answer.
✓
Compute Engine managed instance group
Why this is correct
Managed instance groups can be configured with autoscaling policies that adjust the number of instances based on CPU, load, or custom metrics.
Related concept
Read the scenario before looking for a memorised answer.
✗
Cloud Dataproc
Why it's wrong here
Cloud Dataproc can autoscale clusters but is designed for batch and big data processing, not for serving web traffic.
✗
Cloud SQL
Why it's wrong here
Cloud SQL does not automatically scale compute resources; read replicas and vertical scaling are manual.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse unmanaged instance groups with managed instance groups, assuming both support autoscaling, but only managed instance groups have built-in autoscalers.
Detailed technical explanation
How to think about this question
Compute Engine managed instance groups (MIGs) use autoscalers that monitor utilization metrics (e.g., CPU, load balancing serving capacity) and adjust the number of instances based on policies like target CPU utilization or custom metrics. Cloud Run's autoscaling is driven by the Knative Pod Autoscaler (KPA), which uses a concurrency-based model (default 80 concurrent requests per container instance) to decide when to add or remove instances, and can scale to zero after a configurable idle timeout (default 5 minutes).
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.
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: Cloud Run — Cloud Run is a fully managed serverless compute platform that automatically scales your containerized applications based on incoming traffic, including scaling to zero when there is no traffic. This autoscaling is handled by the Knative serving layer, which adjusts the number of container instances based on request concurrency and CPU utilization.
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.
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 PCD 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 PCD 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.