Quick Answer
The answer is Bounded staleness consistency. This consistency level guarantees write durability across regions by ensuring that replicas lag behind the primary by at most K versions or a time interval T, meaning that even if the primary region fails, all acknowledged writes are preserved and will be replicated to other replicas within that configured staleness window, preventing data loss. On the Microsoft Azure Solutions Architect Expert AZ-305 exam, this scenario tests your understanding of how consistency levels trade off between availability, latency, and durability—specifically that Strong consistency would block writes during a regional failure, while Eventual could lose unpropagated writes. A common trap is assuming Strong consistency is always safest for durability, but Bounded staleness is the correct choice here because it guarantees write durability without requiring synchronous replication across all regions. Memory tip: think “Bounded staleness = bounded data loss window,” meaning you accept a small lag in exchange for guaranteed write survival.
This AZ-305 practice question tests your understanding of design data storage 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.
Your company uses Azure Cosmos DB for a globally distributed application. You need to ensure that writes in one region are not lost if that region fails. Which consistency level should you use to guarantee that writes are durable?
Eventual consistency
Why wrong: Eventual consistency may lose recent writes if a region fails.
Bounded staleness consistency
Bounded staleness provides a guarantee that writes are not lost beyond a configurable staleness.
Strong consistency
Why wrong: Strong consistency is not supported when multi-region writes are enabled.
Consistent prefix consistency
Why wrong: Consistent prefix does not guarantee durability of all writes.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Bounded staleness consistency
Bounded staleness consistency guarantees that writes are durable across regions by ensuring that replicas lag behind the primary by at most K versions or a time interval T. This means that even if a region fails, all acknowledged writes are preserved and will be replicated to other regions within the configured staleness window, preventing data loss.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Eventual consistency
Why it's wrong here
Eventual consistency may lose recent writes if a region fails.
Bounded staleness consistency
Why this is correct
Bounded staleness provides a guarantee that writes are not lost beyond a configurable staleness.
Related concept
Read the scenario before looking for a memorised answer.
Strong consistency
Why it's wrong here
Strong consistency is not supported when multi-region writes are enabled.
Consistent prefix consistency
Why it's wrong here
Consistent prefix does not guarantee durability of all writes.
Common exam traps
The trap here is that candidates often assume strong consistency is required for write durability, but bounded staleness actually provides the same durability guarantee with better performance and availability in globally distributed setups.
Detailed technical explanation
Bounded staleness works by maintaining a 'K' (number of versions) or 'T' (time interval) bound on the lag between the primary and secondary replicas. Under the hood, Cosmos DB uses a multi-master replication protocol with a quorum-based commit; bounded staleness ensures that writes are acknowledged only after they are committed to a majority of replicas within the local region and the staleness bound is not exceeded, providing a balance between consistency and write durability across regions.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
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FAQ
Design data storage solutions — This question tests Design data storage solutions — Read the scenario before looking for a memorised answer..
The correct answer is: Bounded staleness consistency — Bounded staleness consistency guarantees that writes are durable across regions by ensuring that replicas lag behind the primary by at most K versions or a time interval T. This means that even if a region fails, all acknowledged writes are preserved and will be replicated to other regions within the configured staleness window, preventing data loss.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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.
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