The answer is a virtual machine scale set with autoscale, because it is the only Azure service designed to automatically adjust the number of identical VM instances in response to changing CPU usage, which is exactly what a stateless web app requires. A VMSS treats each instance as disposable and interchangeable, so autoscale rules can safely add or remove instances when CPU crosses a defined threshold—such as scaling out at 75% CPU and scaling in when it drops below—without worrying about session state or data persistence. On the AZ-104 exam, this question tests your understanding of compute scaling options; a common trap is choosing Azure App Service autoscale, which works for PaaS but not for managing individual VMs, or selecting a load balancer alone, which distributes traffic but does not add or remove instances. Remember the key distinction: stateless plus CPU-driven scaling equals VMSS with autoscale. A helpful memory tip is “stateless scale set”—if the app doesn’t care which VM it runs on, a scale set is the right fit.
AZ-104 Deploy and Manage Azure Compute Practice Question
This AZ-104 practice question tests your understanding of deploy and manage azure compute. 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 stateless web app on Azure must add or remove instances automatically when CPU usage changes. Which service should you deploy?
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 set with autoscale
A virtual machine scale set (VMSS) with autoscale is the correct choice because it is designed to automatically increase or decrease the number of VM instances based on metrics like CPU usage. Autoscale rules can be configured to scale out when CPU exceeds a threshold (e.g., 75%) and scale in when it drops below a threshold, ensuring the stateless web app handles variable load without manual intervention.
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 set with autoscale
Why this is correct
VM scale sets are designed for multiple identical instances and can scale automatically based on rules.
Related concept
Read the scenario before looking for a memorised answer.
✗
Single virtual machine
Why it's wrong here
A single VM cannot add or remove instances automatically for elastic demand-based scaling.
✗
Availability set
Why it's wrong here
An availability set improves availability, but it does not automatically scale instance count.
✗
Managed disk
Why it's wrong here
A managed disk is a storage resource, not a compute service that scales application instances.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse high-availability constructs (availability sets) or storage components (managed disks) with autoscaling compute, or assume a single VM can be dynamically scaled horizontally, when only VMSS provides automated instance-level scaling based on metrics.
Detailed technical explanation
How to think about this question
Under the hood, VMSS uses Azure Monitor autoscale to evaluate CPU (or other) metrics at regular intervals (default 1 minute) and triggers scale operations via ARM API calls. A key subtlety is that scale-in policies can be configured (e.g., Default, NewestVM, OldestVM) to control which instances are removed, which is critical for stateless apps to avoid disrupting active connections. In a real-world scenario, you might combine VMSS with a load balancer to distribute traffic across instances, ensuring seamless scaling without downtime.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-104 question in full detail.
Deploy and Manage Azure Compute — This question tests Deploy and Manage Azure Compute — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Virtual machine scale set with autoscale — A virtual machine scale set (VMSS) with autoscale is the correct choice because it is designed to automatically increase or decrease the number of VM instances based on metrics like CPU usage. Autoscale rules can be configured to scale out when CPU exceeds a threshold (e.g., 75%) and scale in when it drops below a threshold, ensuring the stateless web app handles variable load without manual intervention.
What should I do if I get this AZ-104 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
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A stateless API must automatically add or remove identical VM instances when CPU usage crosses thresholds. The team also wants Microsoft to distribute instances across fault domains when possible. Which service should the administrator deploy?
medium
A.An availability set
B.Azure Load Balancer
✓ C.A virtual machine scale set
D.Azure App Service
Why C: A virtual machine scale set (VMSS) is the correct choice because it provides built-in autoscaling capabilities that automatically add or remove identical VM instances based on CPU usage thresholds. VMSS also supports automatic distribution of instances across fault domains when configured with a fault domain count greater than 1, meeting the requirement for Microsoft to distribute instances across fault domains.
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Question Discussion
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