AZ-305 Design business continuity solutions Practice Question
A company runs a stateless web application on Azure VMs. They need to ensure the application remains available in the event of an entire Azure datacenter failure. They want to achieve a 99.99% SLA. Which deployment option should they recommend?
⚠ Common exam trap
Many exam-takers confuse Availability Sets (which protect against rack failures) with Availability Zones (which protect against datacenter failures), leading them to choose an option that only provides 99.95% SLA instead of the required 99.99%.
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
✓
B
To survive an entire Azure datacenter failure and achieve a 99.99% SLA, the stateless web application must be deployed across at least two Azure Availability Zones within a region. Availability Zones are physically separate datacenters within the same region, each with independent power, cooling, and networking. Deploying VMs in a zone-redundant configuration ensures that if one datacenter fails, the application continues running in another zone, meeting the 99.99% SLA (which requires a minimum of two zones).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
A
Why it's wrong here
An availability set spreads VMs across fault domains and update domains inside a single Azure datacenter, protecting against host- or rack-level hardware failures. However, if the entire datacenter loses power, cooling, or its network fabric, every fault domain in that datacenter can be affected, so an availability set does not survive a whole-datacenter failure. The SLA for two or more instances in an availability set is only 99.95%, which falls below the required 99.99%.
- ✓
B
Why this is correct
Placing at least two VM instances across two or more Azure availability zones in the same region gives each zone independent power, cooling, and network paths, so a failure of one entire zone or datacenter leaves the other zone(s) serving traffic. This architecture satisfies the Azure Compute SLA of 99.99% connectivity to at least one instance during monthly uptime, and, because the application is stateless, traffic can be load-balanced between zones with no session-stickiness concerns.
- ✗
C
Why it's wrong here
Deploying VMs in a single availability zone does not create high availability, because that zone is a single location for power, cooling, and networking; an entire zone outage takes all VMs in that zone offline. Azure Backup only protects data by creating recoverable snapshots with an RPO and RTO, and restoring from backup requires downtime, so it is a recovery or correctness mechanism, not a high-availability mechanism. Consequently, this design neither protects against a datacenter failure nor meets the 99.99% SLA.
- ✗
D
Why it's wrong here
Using paired Azure regions with Traffic Manager provides disaster recovery for a full regional outage, not high availability inside a single region; Traffic Manager's health probes and DNS failover take minutes to converge, which is too slow for the 99.99% availability target. Azure's 99.99% VM connectivity SLA applies to two or more instances in separate availability zones within the same region, not to geographically replicated deployments, so this option fails the stated requirement.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-305 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-305 exam.