- A
Azure App Service
Why wrong: App Service is a PaaS offering that manages the OS. Customers cannot install custom software or configure the Windows firewall at the OS level. It is suitable for web apps but not for full administrative access.
- B
Azure Virtual Machines
Virtual Machines (IaaS) provide full control over the OS, including installation of custom software, firewall configuration, and high availability through multiple VM instances.
- C
Azure Functions
Why wrong: Functions run code in a serverless environment without exposing the underlying OS. Administrative access is not available.
- D
Azure Container Instances
Why wrong: Container Instances provide isolated containers, but they share the host OS kernel and do not offer full OS administrative access like a virtual machine does.
Quick Answer
The answer is Azure Virtual Machines. This is the correct choice because Azure VMs provide full administrative access to the operating system, including the ability to install custom software, configure firewall rules, and manage the OS kernel—unlike PaaS services like App Services or Azure Functions, which abstract away the OS. By deploying multiple VMs in an availability set or across availability zones, you achieve high availability for the application, meeting the requirement for full OS control and multi-instance redundancy. On the AZ-900 exam, this question tests your ability to distinguish between IaaS (VMs) and PaaS/SaaS offerings; a common trap is choosing Azure App Services, which offers high availability but no OS access. Remember the mnemonic: “VMs give you the keys to the OS, while PaaS locks the door.”
AZ-900 Describe Azure architecture and services Practice Question
This AZ-900 practice question tests your understanding of describe azure architecture and services. 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 company needs to run a custom-built Windows application that requires full administrative access to the operating system, including the ability to install custom software and configure firewall rules. They also need to ensure the application is highly available by running multiple instances. Which Azure compute service should they use?
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
Azure Virtual Machines
Azure Virtual Machines (VMs) provide full administrative access to the operating system, allowing you to install custom software, configure firewall rules, and manage the OS as needed. By deploying multiple VMs in an availability set or across availability zones, you can achieve high availability for the application. This makes VMs the correct choice for a custom Windows application requiring full OS control and multi-instance high availability.
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.
- ✗
Azure App Service
- ✓
Azure Virtual Machines
- ✗
Azure Functions
Why it's wrong here
Functions run code in a serverless environment without exposing the underlying OS. Administrative access is not available.
- ✗
Azure Container Instances
Why it's wrong here
Container Instances provide isolated containers, but they share the host OS kernel and do not offer full OS administrative access like a virtual machine does.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Azure App Service's ability to run custom code with full OS control, but App Service restricts administrative access and does not allow OS-level configuration like firewall rules or custom software installation.
Detailed technical explanation
How to think about this question
Azure VMs run on Hyper-V and give you full control over the guest OS, including the ability to use Windows Firewall with Advanced Security, install third-party drivers, and configure Group Policy. For high availability, you can place VMs in an availability set (which distributes them across fault domains and update domains) or use availability zones (physically separate datacenters within a region) to achieve a 99.99% SLA. This is essential for legacy or custom applications that cannot be refactored to fit a PaaS model.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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: Azure Virtual Machines — Azure Virtual Machines (VMs) provide full administrative access to the operating system, allowing you to install custom software, configure firewall rules, and manage the OS as needed. By deploying multiple VMs in an availability set or across availability zones, you can achieve high availability for the application. This makes VMs the correct choice for a custom Windows application requiring full OS control and multi-instance high availability.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This AZ-900 practice question is part of Courseiva's free Microsoft 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 AZ-900 exam.
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