AZ-204 Certification Practice Question #109

Question

You are developing a Cosmos DB solution that will be deployed to multiple Azure regions.

Your solution must meet the following requirements:

•	Read operations will never receive write operations that are out of order.
•	Maximize concurrency of read operations in all regions.

You need to choose the consistency level for the solution.

Which consistency level should you use?

Accepted Answer

To prevent read operations from seeing out-of-order writes, the consistency level must guarantee Consistent Prefix. The consistency levels that satisfy this are Strong, Bounded Staleness, Session, and Consistent Prefix. To maximize the concurrency of read operations (and minimize latency/maximize availability) across multiple regions, we should choose the weakest consistency level that satisfies this requirement, which is Consistent Prefix. Eventual consistency is weaker but does not guarantee in-order reads.

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