AZ-900 Describe Azure architecture and services Practice Question
Which Azure compute service runs identical VM instances in multiple Availability Zones with automatic load balancing?
⚠ Common exam trap
Watch out — candidates often confuse Availability Sets (which only protect within a single datacenter) with Availability Zones (which protect across datacenters), leading them to select Option A even though it lacks both multi-zone distribution and automatic load balancing.
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 Machine Scale Sets across Availability Zones
Azure Virtual Machine Scale Sets (VMSS) can be configured to span multiple Availability Zones, automatically distributing VM instances across those zones for high availability. When combined with an Azure Load Balancer or Application Gateway, the scale set provides automatic load balancing of incoming traffic across all instances, meeting the requirement exactly.
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 Sets
Why it's wrong here
Azure Availability Sets work within a single datacenter and provide high availability by distributing VMs across fault and update domains to protect against hardware failures and planned maintenance. However, they do not support automatic scaling, and because they are confined to one datacenter, they cannot provide zone-level redundancy. Azure Virtual Machine Scale Sets, in contrast, can be deployed across Availability Zones to deliver both auto-scaling and cross-zone resilience.
- ✓
Azure Virtual Machine Scale Sets across Availability Zones
Why this is correct
Azure Virtual Machine Scale Sets (VMSS) deployed across Availability Zones provide a zone-redundant group of identical VMs that can automatically scale in and out based on demand or a schedule. When configured with an Azure Load Balancer or Application Gateway, traffic is distributed across VMs in different zones, ensuring the application remains available even if an entire zone fails. This makes VMSS the correct choice because it combines auto-scaling with cross-zone high availability.
- ✗
Azure Dedicated Host
Why it's wrong here
Azure Dedicated Host provides physical servers dedicated to your workloads, giving you control over host maintenance and compliance for licensing or security requirements. However, it does not provide automatic scaling of VMs, and a dedicated host is typically pinned to a single availability zone, so it cannot distribute VM instances across zones to achieve zone redundancy. You would need to manually provision and manage VMs across multiple hosts to build cross-zone availability.
- ✗
Azure Batch
Why it's wrong here
Azure Batch is a managed service for running large-scale parallel and high-performance computing jobs by scheduling tasks onto a pool of VMs. It is not designed to host a continuously running application with automatic scaling across Availability Zones in the same way VMSS does. While Batch pools can scale, the service focuses on job execution rather than providing a general-purpose, zone-redundant group of always-on VMs behind a load balancer.
Go deeper
Related to this question
Learn chapter
Azure Regions and Geographies
Key term
High availability
High availability is a system design approach that aims to keep applications and services operational and accessible with minimal downtime, even when some components fail.
Key term
Azure Load Balancer
Azure Load Balancer is a cloud service that evenly distributes incoming network traffic across multiple virtual machines or resources to ensure reliability and high availability.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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