- A
Fault domains
Why wrong: Fault domains protect VMs from hardware failures by placing them in different server racks, but they do not control which VMs are updated during planned maintenance.
- B
Update domains
Update domains ensure that VMs are updated sequentially during planned maintenance. By assigning VMs to different update domains, Azure updates only one update domain at a time, maintaining the required availability.
- C
Proximity placement groups
Why wrong: Proximity placement groups are used to co-locate VMs for low network latency, not to manage maintenance updates or availability during platform updates.
- D
Availability zones
Why wrong: Availability zones are physically separate datacenters within a region and are not a component of an availability set. They provide high availability across datacenters, but the question specifically asks about the component within an availability set that handles maintenance updates.
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 two Azure virtual machines in an availability set. The application requires that at least one VM remains running during Azure platform-initiated maintenance, such as operating system updates to the underlying host. Which component of the availability set directly ensures that the VMs are not updated at the same time?
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
Update domains
Update domains (B) are the correct component because they logically group VMs that are updated together during Azure platform-initiated maintenance. By placing VMs in different update domains, Azure ensures that only one update domain is taken offline at a time, guaranteeing that at least one VM remains running during host OS updates.
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.
- ✗
Fault domains
Why it's wrong here
Fault domains protect VMs from hardware failures by placing them in different server racks, but they do not control which VMs are updated during planned maintenance.
- ✓
Update domains
Why this is correct
Update domains ensure that VMs are updated sequentially during planned maintenance. By assigning VMs to different update domains, Azure updates only one update domain at a time, maintaining the required availability.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Proximity placement groups
Why it's wrong here
Proximity placement groups are used to co-locate VMs for low network latency, not to manage maintenance updates or availability during platform updates.
- ✗
Availability zones
Why it's wrong here
Availability zones are physically separate datacenters within a region and are not a component of an availability set. They provide high availability across datacenters, but the question specifically asks about the component within an availability set that handles maintenance updates.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse fault domains (hardware failure isolation) with update domains (maintenance sequencing), leading them to incorrectly select fault domains when the question specifically asks about platform-initiated maintenance updates.
Detailed technical explanation
How to think about this question
Azure availability sets support up to 20 update domains by default (configurable up to 20), and during planned maintenance, Azure reboots VMs one update domain at a time, waiting 30 minutes between domains to allow application recovery. This sequential update process is critical for applications that require high availability, as it ensures that even if one VM fails during an update, the other VMs in different update domains remain operational.
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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Describe Azure architecture and services — study guide chapter
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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: Update domains — Update domains (B) are the correct component because they logically group VMs that are updated together during Azure platform-initiated maintenance. By placing VMs in different update domains, Azure ensures that only one update domain is taken offline at a time, guaranteeing that at least one VM remains running during host OS updates.
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.
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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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