AZ-104 Deploy and Manage Azure Compute Practice Question
A stateless web service runs on identical VMs and must keep serving traffic if Microsoft takes one datacenter out of service in the region. The load must also scale out automatically during peak hours, and instances should be spread across independent zone boundaries. Which two configurations should the administrator use? Select two.
⚠ Common exam trap
Candidates often confuse Availability Sets (which protect against rack-level failures within one datacenter) with Availability Zones (which protect against full datacenter outages), leading them to select Availability Set instead of Availability Zones for cross-datacenter resilience.
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
✓
Virtual machine scale set
A is correct because Virtual Machine Scale Sets (VMSS) provide built-in autoscaling capabilities that automatically adjust the number of VM instances based on demand (e.g., CPU or memory metrics), ensuring the web service scales out during peak hours. Additionally, VMSS supports spreading instances across availability zones, which protects against a single datacenter failure by distributing VMs across independent zone boundaries within a region.
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
Why this is correct
A virtual machine scale set is correct because it is designed to run a stateless web service on a fleet of identical VM instances. It automatically scales out and in based on CPU, memory, or custom metrics, distributes traffic via a load balancer, and replaces unhealthy instances using health probes, making it the optimal compute model for this workload.
- ✓
Availability zones
Why this is correct
Availability zones are correct because they physically isolate each VM in its own datacenter with independent power, cooling, and networking, so a single datacenter failure cannot take down the entire service. Combining zones with a scale set is the recommended pattern for regional resilience, but zones alone do not provide automatic scaling.
- ✗
Availability set
Why it's wrong here
An availability set is wrong here because it only spreads VMs across fault and update domains within a single Azure datacenter, protecting against hardware failure and planned maintenance, not against an entire zone or datacenter outage. It also lacks the auto-scaling capability needed to handle variable load on a stateless web tier.
When this WOULD be correct
For a multi-tier application where VMs must be placed in separate fault domains and update domains within a single datacenter to protect against hardware failures and planned maintenance, while not requiring cross-datacenter redundancy or auto-scaling.
- ✗
Proximity placement group
Why it's wrong here
A proximity placement group is wrong because it intentionally places VMs as close together as possible to minimize network latency, which concentrates failure risk rather than spreading it across zones. It is used for latency-sensitive workloads like HPC or tightly coupled tiers, not for scalable, resilient stateless web servers.
When this WOULD be correct
A question requiring low-latency communication between VMs in a tightly coupled application (e.g., HPC or latency-sensitive workloads) where all VMs must be in the same datacenter to minimize network latency, and fault tolerance is not the primary concern.
- ✗
Dedicated host
Why it's wrong here
A dedicated host is wrong because it allocates physical servers exclusively for your VMs, but all VMs on that host share the same physical hardware, so a host failure affects them all. It does not provide auto-scaling or data-center-level redundancy, and it is unnecessary for a stateless web service.
When this WOULD be correct
A question requiring compliance with licensing agreements that tie to specific physical servers, or needing to guarantee VM placement on dedicated hardware for regulatory reasons, would make dedicated hosts the correct answer.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The AZ-104 exam frequently reuses these exact scenarios with slightly different constraints.
✓Virtual machine scale setCorrect answer▾
Why this is correct
A virtual machine scale set is correct because it is designed to run a stateless web service on a fleet of identical VM instances. It automatically scales out and in based on CPU, memory, or custom metrics, distributes traffic via a load balancer, and replaces unhealthy instances using health probes, making it the optimal compute model for this workload.
✗Availability setWrong answer — click to see why▾
Why this is wrong here
An availability set only protects against rack-level failures within a single datacenter, not against an entire datacenter outage. It also does not support automatic scaling.
★ When this WOULD be the correct answer
For a multi-tier application where VMs must be placed in separate fault domains and update domains within a single datacenter to protect against hardware failures and planned maintenance, while not requiring cross-datacenter redundancy or auto-scaling.
Why candidates choose this
Candidates may confuse availability sets with availability zones, thinking both provide datacenter-level redundancy, or they may overlook the requirement for automatic scaling and focus only on high availability.
✗Proximity placement groupWrong answer — click to see why▾
Why this is wrong here
Proximity placement groups reduce network latency by keeping VMs close together, but they do not provide fault isolation across independent zone boundaries or automatic scaling, which are required for high availability and auto-scaling across datacenters.
★ When this WOULD be the correct answer
A question requiring low-latency communication between VMs in a tightly coupled application (e.g., HPC or latency-sensitive workloads) where all VMs must be in the same datacenter to minimize network latency, and fault tolerance is not the primary concern.
Why candidates choose this
Candidates may confuse proximity placement groups with availability zones, thinking that grouping VMs close together ensures high availability, but they fail to recognize that proximity groups actually increase risk by placing VMs in the same failure domain.
✗Dedicated hostWrong answer — click to see why▾
Why this is wrong here
Dedicated hosts provide physical server isolation for compliance or licensing, but do not offer automatic scaling or distribution across independent zone boundaries, which are required for high availability and auto-scaling in this scenario.
★ When this WOULD be the correct answer
A question requiring compliance with licensing agreements that tie to specific physical servers, or needing to guarantee VM placement on dedicated hardware for regulatory reasons, would make dedicated hosts the correct answer.
Why candidates choose this
Candidates may think dedicated hosts improve reliability or availability, but they actually focus on hardware isolation, not fault tolerance across datacenters or auto-scaling.
Analysis generated from the official AZ-104blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Go deeper
Related to this question
Learn chapter
Microsoft Entra ID Users and Groups
Key term
Availability
Availability is the measure of how often a system or service is operational and accessible when needed, typically expressed as a percentage of uptime.
Key term
Region
A region is a distinct geographic location where a cloud provider operates multiple data centers that are connected by low-latency networks and provide cloud services.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-104 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-104 exam.