You plan to create an Azure Cosmos DB for NoSQL account that will have a single write region and three read regions.
You need to set the consistency level for the account. The solution must meet the following requirements:
• In the write region, writes must replicate synchronously across at least three replicas.
• In the read regions, reads must see writes in order for transactional batches.
• Throughput for reads and writes must be maximized.
Which consistency level should you select?
For the given requirements, the consistency level must ensure synchronous replication for writes across at least three replicas in the write region and that reads see writes in order for transactional batches, while maximizing throughput. Strong consistency guarantees that every read receives the most recent write, which aligns with synchronous replication and the need for transactional batch ordering. It also ensures linearizability, meaning all writes are synchronously replicated and visible to the readers in the same order. Thus, Strong consistency is the appropriate choice.
In the write region, writes must replicate synchronously across at least three replicas. Only the Strong consistency provides the synch writing, all others are async. Therefore Strong is the answer.
Strong: Ensures that reads always return the most recent write. Provides a linearizability guarantee, meaning writes are synchronously replicated to all replicas before acknowledgment. Ensures that reads are guaranteed to see the most recent writes, which aligns with the requirement for transactional batches.
Why not Consistent Prefix: reads must appear in order, and throughput must be maximized, which is not the case with Strong. In every region, writes are done to 3 replicas automatically.