- A
Locally redundant storage (LRS)
Why wrong: LRS replicates data three times within a single physical datacenter in the same region. If that datacenter fails, all replicas are lost, so it does not meet the requirement to withstand a datacenter failure.
- B
Zone-redundant storage (ZRS)
ZRS replicates data synchronously across three Azure availability zones within the same region. Each availability zone is a separate datacenter. This protects against a single datacenter failure, keeps data within the East US region, and is less expensive than geo-redundant options. This meets all requirements.
- C
Geo-redundant storage (GRS)
Why wrong: GRS replicates data to a secondary region that is geographically paired (e.g., East US pairs with West US). While it protects against a regional disaster, it copies data outside the East US region, which may increase cost and is not necessary for the stated requirement of staying within the single region.
- D
Read-access geo-redundant storage (RA-GRS)
Why wrong: RA-GRS is identical to GRS but also provides read access to the secondary region. Like GRS, it replicates data to a different region, which is not required and incurs additional cost. It does not meet the 'within East US' constraint.
AZ-900 Describe Azure architecture and services Practice Question
This AZ-900 practice question tests your understanding of describe azure architecture and services. 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 stores a critical database in Azure Blob Storage. The data must remain available even if an entire Azure datacenter fails. The company uses the East US region, which supports availability zones. They want the lowest-cost storage redundancy option that protects against a full datacenter failure while keeping all data within the East US region. Which redundancy option should they choose?
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
Zone-redundant storage (ZRS)
Zone-redundant storage (ZRS) is the correct choice because it synchronously replicates data across three availability zones within the East US region, ensuring data remains accessible even if an entire datacenter (one zone) fails. This meets the requirement for intra-region protection against a full datacenter failure at the lowest cost, as ZRS does not incur the additional expense of geo-replication.
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.
- ✗
Locally redundant storage (LRS)
Why it's wrong here
LRS replicates data three times within a single physical datacenter in the same region. If that datacenter fails, all replicas are lost, so it does not meet the requirement to withstand a datacenter failure.
- ✓
Zone-redundant storage (ZRS)
Why this is correct
ZRS replicates data synchronously across three Azure availability zones within the same region. Each availability zone is a separate datacenter. This protects against a single datacenter failure, keeps data within the East US region, and is less expensive than geo-redundant options. This meets all requirements.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Geo-redundant storage (GRS)
Why it's wrong here
GRS replicates data to a secondary region that is geographically paired (e.g., East US pairs with West US). While it protects against a regional disaster, it copies data outside the East US region, which may increase cost and is not necessary for the stated requirement of staying within the single region.
- ✗
Read-access geo-redundant storage (RA-GRS)
Why it's wrong here
RA-GRS is identical to GRS but also provides read access to the secondary region. Like GRS, it replicates data to a different region, which is not required and incurs additional cost. It does not meet the 'within East US' constraint.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse ZRS with GRS, thinking geo-redundancy is required for any datacenter failure, but the question explicitly limits data to the East US region, making ZRS the correct and lowest-cost option for intra-region datacenter failure protection.
Detailed technical explanation
How to think about this question
ZRS uses synchronous replication across three distinct availability zones within the same region, each with independent power, cooling, and networking, providing a Recovery Point Objective (RPO) of zero and a Recovery Time Objective (RTO) typically within minutes. Under the hood, Azure Blob Storage with ZRS writes data to all three zones before acknowledging the write, ensuring strong consistency. In a real-world scenario, if a zone suffers a catastrophic failure (e.g., fire or flood), ZRS allows immediate failover to the remaining zones without manual intervention, unlike LRS which would require restoring from backup.
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
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this AZ-900 question test?
Describe Azure architecture and services — This question tests Describe Azure architecture and services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Zone-redundant storage (ZRS) — Zone-redundant storage (ZRS) is the correct choice because it synchronously replicates data across three availability zones within the East US region, ensuring data remains accessible even if an entire datacenter (one zone) fails. This meets the requirement for intra-region protection against a full datacenter failure at the lowest cost, as ZRS does not incur the additional expense of geo-replication.
What should I do if I get this AZ-900 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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Last reviewed: Jun 11, 2026
This AZ-900 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-900 exam.
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