Question 191 of 1,031

Describe Azure architecture and services →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is Virtual Machine Scale Sets. This Azure compute service is the correct choice because it enables autoscaling virtual machines with load balancer health probes, automatically adding instances when CPU exceeds 80% and removing them when it drops below 30%, while also integrating with Azure Load Balancer to immediately stop routing traffic to any failed VM detected by health probes. On the Microsoft Azure Fundamentals AZ-900 exam, this question tests your understanding of how VMSS combines scaling rules and health monitoring into a single managed solution, often appearing as a scenario-based question where you must distinguish it from standalone virtual machines or availability sets. A common trap is choosing Azure Load Balancer alone, but remember that the load balancer only distributes traffic—it does not scale VMs. Memory tip: think "Scale Sets = Scaling + Health Sets," where the health probes are built into the scaling logic for seamless traffic management.

AZ-900 Describe Azure architecture and services Practice Question

This AZ-900 practice question tests your understanding of describe azure architecture and services. 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 company runs a customer-facing e-commerce platform on multiple Azure virtual machines behind a load balancer. The platform experiences unpredictable traffic spikes during promotions. The operations team needs a solution that automatically adds new virtual machines when CPU utilization exceeds 80% and removes virtual machines when utilization drops below 30%. The solution must also ensure that if a virtual machine fails, the load balancer immediately stops routing traffic to it. Which Azure compute service should the team use?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "immediately / without restart"
Why it matters: Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.

Question 1mediummultiple choice

Review the full routing breakdown →

A
Virtual Machine Scale Sets
Correct. VMSS enables autoscaling based on performance metrics and integrates with load balancer health probes to automatically remove failed instances from traffic routing.
B
Azure App Service
Why wrong: Incorrect. Azure App Service is a PaaS offering for web applications that does support autoscaling, but the scenario explicitly requires managing virtual machines and a load balancer. App Service abstracts away the VMs, so it is not the appropriate solution here.
C
Availability Sets
Why wrong: Incorrect. Availability Sets protect against hardware failures and maintenance events by distributing VMs across fault domains and update domains, but they do not provide autoscaling or the ability to automatically add/remove VMs based on load.
D
Azure Batch
Why wrong: Incorrect. Azure Batch is designed for large-scale parallel and high-performance computing jobs, not for running a continuously available web application with live autoscaling based on CPU usage.

Full breakdown with real-world context →

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

✓

Virtual Machine Scale Sets

Virtual Machine Scale Sets (VMSS) provide automatic scaling based on metrics like CPU utilization, enabling the platform to add VMs when CPU exceeds 80% and remove VMs when it drops below 30%. Additionally, VMSS integrates with Azure Load Balancer to automatically detect VM failures via health probes and immediately stop routing traffic to unhealthy instances, meeting all stated requirements.

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.

✓
Virtual Machine Scale Sets
Why this is correct
Correct. VMSS enables autoscaling based on performance metrics and integrates with load balancer health probes to automatically remove failed instances from traffic routing.
Clue confirmation
The clue word "immediately / without restart" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Azure App Service
Why it's wrong here
Incorrect. Azure App Service is a PaaS offering for web applications that does support autoscaling, but the scenario explicitly requires managing virtual machines and a load balancer. App Service abstracts away the VMs, so it is not the appropriate solution here.
✗
Availability Sets
Why it's wrong here
Incorrect. Availability Sets protect against hardware failures and maintenance events by distributing VMs across fault domains and update domains, but they do not provide autoscaling or the ability to automatically add/remove VMs based on load.
✗
Azure Batch
Why it's wrong here
Incorrect. Azure Batch is designed for large-scale parallel and high-performance computing jobs, not for running a continuously available web application with live autoscaling based on CPU usage.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often confuse Availability Sets (which only provide fault-domain redundancy) with the autoscaling and health-probe-based traffic management that only Virtual Machine Scale Sets provide.

Trap categories for this question

Scenario analysis trap
Incorrect. Azure App Service is a PaaS offering for web applications that does support autoscaling, but the scenario explicitly requires managing virtual machines and a load balancer. App Service abstracts away the VMs, so it is not the appropriate solution here.

Detailed technical explanation

How to think about this question

VMSS uses an autoscale engine that evaluates metrics like Percentage CPU (from the Azure Diagnostics Extension or VM Insights) against defined rules, and triggers scale-out or scale-in operations by creating or deleting VM instances from a configured VM image. The integration with Azure Load Balancer relies on health probes (e.g., HTTP or TCP probes) that check instance health; if a probe fails consecutively (default 2 failures), the load balancer removes the VM from the backend pool, and VMSS can optionally automatically repair or replace the failed instance via the 'automatic repairs' policy.

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.

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FAQ

Questions learners often ask

What does this AZ-900 question test?

Describe Azure architecture and services — This question tests Describe Azure architecture and services — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Virtual Machine Scale Sets — Virtual Machine Scale Sets (VMSS) provide automatic scaling based on metrics like CPU utilization, enabling the platform to add VMs when CPU exceeds 80% and remove VMs when it drops below 30%. Additionally, VMSS integrates with Azure Load Balancer to automatically detect VM failures via health probes and immediately stop routing traffic to unhealthy instances, meeting all stated requirements.

What should I do if I get this AZ-900 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: "immediately / without restart". Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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