The answer is deploying VMs across at least two Azure Availability Zones. This is correct because Availability Zones are physically separate datacenters within a single Azure region, each with independent power, cooling, and networking, so if an entire datacenter fails, the stateless web application continues running in another zone, which is the only way to achieve the 99.99% SLA. On the AZ-305 exam, this tests your understanding of high-level resiliency patterns versus regional redundancy—a common trap is confusing Availability Zones with Availability Sets, which only protect against rack-level failures within a single datacenter, not a full datacenter outage. Remember that for datacenter failure protection, you need zone-level separation, not just fault domain distribution. A quick memory tip: think "Zones = Zero downtime from a single datacenter disaster."
AZ-305 Design business continuity solutions Practice Question
This AZ-305 practice question tests your understanding of design business continuity solutions. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
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?
Why wrong: An availability set spreads VMs across fault domains within a single datacenter. It protects against rack failures but not an entire datacenter failure.
B
B
Deploying VMs across at least two availability zones in the same region protects against an entire datacenter failure and meets the 99.99% SLA.
C
C
Why wrong: Placing VMs in a single zone does not protect against a datacenter failure, and Azure Backup only provides data recovery, not high availability.
D
D
Why wrong: Deploying across paired regions with Traffic Manager provides disaster recovery, not high availability within the region. It may not meet the 99.99% SLA due to failover time.
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).
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 within a single datacenter. It protects against rack failures but not an entire datacenter failure.
✓
B
Why this is correct
Deploying VMs across at least two availability zones in the same region protects against an entire datacenter failure and meets the 99.99% SLA.
Related concept
Read the scenario before looking for a memorised answer.
✗
C
Why it's wrong here
Placing VMs in a single zone does not protect against a datacenter failure, and Azure Backup only provides data recovery, not high availability.
✗
D
Why it's wrong here
Deploying across paired regions with Traffic Manager provides disaster recovery, not high availability within the region. It may not meet the 99.99% SLA due to failover time.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often 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%.
Detailed technical explanation
How to think about this question
Azure Availability Zones are unique physical locations within an Azure region, each with one or more datacenters. To achieve a 99.99% SLA for VMs, you must deploy at least two instances across two or more zones and ensure they are in the same availability set or use a load balancer. The 99.99% SLA is calculated based on the combined uptime of all instances; if one zone fails, the other continues serving traffic. This design also requires the application to be stateless so that session data is not lost during a zone failure.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-305 question in full detail.
Design business continuity solutions — This question tests Design business continuity solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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).
What should I do if I get this AZ-305 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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