AZ-900 Describe Azure architecture and services Practice Question
What is the purpose of Azure Availability Zones?
⚠ Common exam trap
Many candidates confuse Availability Zones (which protect against datacenter failures within a region) with Azure Region Pairs (which protect against region-wide disasters by replicating data across geographically separated regions).
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
✓
To provide fault isolation against datacenter-level failures within a region
Azure Availability Zones are physically separate datacenters within an Azure region, each with independent power, cooling, and networking. By placing VMs or other resources across multiple zones, you protect your application from a single datacenter failure, ensuring high availability and fault isolation at the datacenter level within the 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.
- ✗
To reduce the latency of content delivery to global users
Why it's wrong here
Availability Zones do not cache content or place compute edge nodes closer to global users; they exist inside a single region. Latency reduction for worldwide audiences is accomplished with Azure Content Delivery Network (CDN) or Azure Front Door, which use globally distributed edge points of presence. Zone redundancy focuses on uptime and fault tolerance, not on minimizing network round-trip times.
- ✓
To provide fault isolation against datacenter-level failures within a region
Why this is correct
Availability Zones are unique physical locations with independent power, cooling, and networking within an Azure region, creating fault isolation from a datacenter-scale failure. By deploying resources across multiple zones, an application can continue operating if one entire datacenter is disrupted, which is the core high-availability benefit these zones provide. This is why Availability Zones are the correct answer for protecting against datacenter-level failures within a region.
- ✗
To connect on-premises networks to Azure securely
Why it's wrong here
Availability Zones are physically separate datacenters within a single Azure region, designed for high availability, not for establishing hybrid connectivity. Secure connections from on-premises networks to Azure are provided by VPN Gateway (IPsec over the internet) or ExpressRoute (private dedicated connection). These services are unrelated to zone-based fault isolation, which protects workloads inside the region.
- ✗
To replicate data automatically between Azure regions
Why it's wrong here
Availability Zones operate only within one region, so they cannot replicate data across multiple Azure regions. Cross-region data replication is delivered by features like geo-redundant storage (GRS) or Azure Site Recovery to a paired region. This distinction matters because zones guard against a single datacenter failure, whereas geographic replication protects against a whole regional outage.
Go deeper
Related to this question
Learn chapter
Azure Regions and Geographies
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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