Quick Answer
The answer is unlimited because an availability set does not impose a hard cap on the number of VMs you can add; instead, it logically distributes VMs across fault domains and update domains to maximize fault tolerance. With 3 fault domains and 5 update domains, Azure ensures that each VM is placed into a different fault domain and update domain as they are added, but there is no limit on how many VMs can be accommodated—the distribution simply repeats across the available slots. On the Microsoft Azure Solutions Architect Expert AZ-305 exam, this concept tests your understanding that availability set fault domains and update domains are about physical separation, not capacity limits; a common trap is assuming a VM limit based on the number of fault domains (e.g., 3 VMs) or update domains (e.g., 5 VMs). The key memory tip: think of an availability set as a parking lot with labeled spaces—you can park as many cars as you want, but each car gets its own designated spot for safety, and the lot never runs out of spaces.
This AZ-305 practice question tests your understanding of design infrastructure solutions. 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.
Your organization is deploying a critical application on Azure virtual machines. You need to ensure that the VMs are distributed across multiple fault domains and update domains within an availability set. You create an availability set with 3 fault domains and 5 update domains. How many VMs can you add to this availability set to maximize fault tolerance?
5 VMs
Why wrong: You can add more than 5 VMs; update domains are used for distribution.
Unlimited
There is no maximum number of VMs in an availability set; you can add as many as your subscription allows.
15 VMs
Why wrong: This number is not a limit; you can add many more.
3 VMs
Why wrong: You can add more than 3 VMs; fault domains are used for distribution.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Unlimited
Option D is correct. There is no limit on the number of VMs you can add to an availability set, but to maximize fault tolerance, you should add as many VMs as needed; the fault domains and update domains will be used to distribute them. The question asks for the number of VMs you can add, which is unlimited (subject to subscription limits). Options A, B, and C are incorrect because they imply a limit.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
5 VMs
Why it's wrong here
You can add more than 5 VMs; update domains are used for distribution.
Unlimited
Why this is correct
There is no maximum number of VMs in an availability set; you can add as many as your subscription allows.
Related concept
Read the scenario before looking for a memorised answer.
15 VMs
Why it's wrong here
This number is not a limit; you can add many more.
3 VMs
Why it's wrong here
You can add more than 3 VMs; fault domains are used for distribution.
Common exam traps
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
Identify which AZ-305 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Design infrastructure solutions — This question tests Design infrastructure solutions — Read the scenario before looking for a memorised answer..
The correct answer is: Unlimited — Option D is correct. There is no limit on the number of VMs you can add to an availability set, but to maximize fault tolerance, you should add as many VMs as needed; the fault domains and update domains will be used to distribute them. The question asks for the number of VMs you can add, which is unlimited (subject to subscription limits). Options A, B, and C are incorrect because they imply a limit.
Identify which AZ-305 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 20, 2026
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