Exam AZ-204 topic 3 question 58 discussion

What we can rule out is B eventual, since there can be out-of-order reads, and C, since the question does not contain any information about a boundary. If the wording of the question was "consistency" instead of "concurrency", I would go for A "session". Therefore I'd expect the lower the consistency, the higher the concurrency. I would go for D Consistent prefix. Reference: https://learn.microsoft.com/en-us/azure/cosmos-db/consistency-levels No words about concurrency there.

Since consistent prefix allows for a consistent read for e.g. 2 write operations (documents aren’t returned in mixed versions), then same applies for 3, 4, 5 etc., which means more write operations can be done in parallel. Hence the answer D, consistent prefix allows for bigger concurrency.

ChatGPT response: Consistent prefix.

After reading the documentation I fully agree with de55d65's explanation and choose D as well.

C. bounded staleness: Bounded staleness consistency ensures that reads never see out-of-order writes and provides a lag window within which the data might be stale. This consistency level guarantees that reads are consistent within a specified staleness window, which meets the requirement of never receiving out-of-order writes. It also allows for high concurrency of read operations across multiple regions.

C is the correct answer Bounded staleness guarantees that read operations will never see writes out of order, which directly addresses your requirement for ensuring that read operations never receive write operations that are out of order. It also maximizes the concurrency of read operations in multiple regions while providing a guarantee that reads lag behind writes by a certain staleness window (defined in terms of time or number of versions). This balance between consistency and availability fits your scenario well.

"Consistent prefix consistency, the reads never see out of order writes for a transactional batch of writes" https://learn.microsoft.com/en-us/azure/cosmos-db/consistency-levels

Why not C?