- A
Azure Availability Zone
Why wrong: Availability Zones protect against an entire datacenter outage within a region by placing VMs in physically separate zones, but they do not control the sequencing of updates during planned maintenance. Zonal VMs are still subject to individual zone updates. Therefore, this does not guarantee that VMs are updated in separate batches.
- B
Azure Availability Set
Availability Sets logically group VMs into update domains and fault domains. Update domains ensure that only a subset of VMs is taken offline during planned Azure platform maintenance, preventing simultaneous downtime. Fault domains distribute VMs across separate hardware racks to guard against local hardware failures. This meets the requirement of keeping at least two VMs running during updates.
- C
Azure Virtual Machine Scale Set
Why wrong: Virtual Machine Scale Sets are primarily used to automatically scale the number of VM instances based on demand. While they do support update domains for rolling upgrades, they introduce unnecessary complexity for a fixed set of three VMs that only need grouping for high availability. An Availability Set is the simpler, appropriate solution.
- D
Azure Site Recovery
Why wrong: Azure Site Recovery is a disaster recovery service that replicates workloads to a secondary region to protect against region-wide outages. It does not address planned maintenance events within the primary region and cannot ensure that VMs are updated in separate batches.
AZ-900 Describe Azure architecture and services Practice Question
This AZ-900 practice question tests your understanding of describe azure architecture and services. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 deploys three Azure virtual machines (VMs) that host a critical line-of-business application. All three VMs are located in the same Azure region. The company notices that during planned maintenance events triggered by the Azure platform, such as host OS updates, all three VMs are updated simultaneously, causing the application to become unavailable. The company requires that during such maintenance, at least two VMs remain running to preserve application uptime. Which Azure feature should the company implement to logically group the VMs and ensure they are updated in separate batches?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"least"Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
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 Availability Set
An Azure Availability Set logically groups VMs to protect against platform updates and faults. By placing VMs into an availability set, Azure assigns them to different update domains (default 5) and fault domains (default 2). During planned maintenance, only one update domain is rebooted at a time, ensuring that at most one of the three VMs is updated simultaneously, thus keeping at least two VMs running.
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 Availability Zone
Why it's wrong here
Availability Zones protect against an entire datacenter outage within a region by placing VMs in physically separate zones, but they do not control the sequencing of updates during planned maintenance. Zonal VMs are still subject to individual zone updates. Therefore, this does not guarantee that VMs are updated in separate batches.
- ✓
Azure Availability Set
Why this is correct
Availability Sets logically group VMs into update domains and fault domains. Update domains ensure that only a subset of VMs is taken offline during planned Azure platform maintenance, preventing simultaneous downtime. Fault domains distribute VMs across separate hardware racks to guard against local hardware failures. This meets the requirement of keeping at least two VMs running during updates.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Azure Virtual Machine Scale Set
Why it's wrong here
Virtual Machine Scale Sets are primarily used to automatically scale the number of VM instances based on demand. While they do support update domains for rolling upgrades, they introduce unnecessary complexity for a fixed set of three VMs that only need grouping for high availability. An Availability Set is the simpler, appropriate solution.
- ✗
Azure Site Recovery
Why it's wrong here
Azure Site Recovery is a disaster recovery service that replicates workloads to a secondary region to protect against region-wide outages. It does not address planned maintenance events within the primary region and cannot ensure that VMs are updated in separate batches.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Availability Zones with Availability Sets, thinking that zones provide the same update batching behavior, but zones only guarantee physical separation across data centers, not the sequential update domain logic that ensures VMs are updated in separate batches during planned maintenance.
Detailed technical explanation
How to think about this question
An availability set uses update domains (UDs) and fault domains (FDs) to distribute VMs. By default, Azure assigns up to 5 UDs (configurable up to 20) and 2 FDs. During planned maintenance, Azure reboots VMs one UD at a time, with a 30-minute delay between UDs to allow application recovery. This ensures that only VMs in the same UD are updated together, so with 3 VMs in an availability set, at most 2 VMs could be in the same UD, but typically they are spread across UDs 0, 1, and 2, leaving at least 2 VMs running.
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.
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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 Availability Set — An Azure Availability Set logically groups VMs to protect against platform updates and faults. By placing VMs into an availability set, Azure assigns them to different update domains (default 5) and fault domains (default 2). During planned maintenance, only one update domain is rebooted at a time, ensuring that at most one of the three VMs is updated simultaneously, thus keeping at least two VMs running.
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: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
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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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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