AZ-305 Design data storage solutions Practice Question
A globally distributed application requires multi-region writes to a NoSQL database and must tolerate regional write outages. Which Azure service capability should be selected?
⚠ Common exam trap
Many candidates confuse geo-redundant storage options (like RA-GRS or GRS) with active-active multi-region write capabilities, not realizing that most Azure storage services (including Table Storage and Files) only support writes to a single primary region, whereas Cosmos DB is the only service that natively supports multi-region writes.
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
✓
Azure Cosmos DB multi-region writes
Azure Cosmos DB multi-region writes is the correct choice because it provides active-active replication across multiple Azure regions, enabling writes to be accepted in any configured region and automatically replicated. This design ensures that if one region experiences a write outage, the application can continue writing to other regions without interruption, meeting the requirement for multi-region writes and regional write outage tolerance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Azure Table Storage RA-GRS
Why it's wrong here
RA-GRS for Azure Table Storage replicates data to a secondary region using geo-redundant storage, but that secondary endpoint is read-only. While RA-GRS allows read access during an outage, it does not accept writes in the secondary region, nor does it provide any active-active multi-master capability. Azure Table Storage remains a region-scoped key-value store, not a multi-writer globally distributed database, so it cannot meet a multi-region write requirement.
- ✗
Azure SQL Database serverless only
Why it's wrong here
Azure SQL Database serverless is specifically an auto-scaling compute tier that pauses idle databases to reduce cost, not a replication or write-availability feature. When serverless is used with active geo-replication, it still maintains a single writable primary; readable secondaries in other regions cannot accept writes and require failover to promote one to primary. This mode enables geo-redundancy and read scale-out, but it does not support simultaneous multi-region writes, which make it incorrect for this requirement.
- ✓
Azure Cosmos DB multi-region writes
Why this is correct
Azure Cosmos DB with multi-region writes enables active-active replication where every region assigned to the account is writable, allowing any region to accept write requests with configurable conflict resolution (e.g., Last-Writer-Wins or custom). Each write is replicated to all other regions asynchronously while the chosen consistency level (such as bounded staleness or eventual) is honored at the client. This architecture provides high write availability, low latency for globally distributed applications, and is the only listed option that natively supports multi-region writes.
- ✗
Azure Files geo-redundant storage
Why it's wrong here
Azure Files geo-redundant storage (GRS or GZRS) replicates the file share to a paired secondary region for disaster recovery, but the secondary copy is read-only and cannot be written to concurrently. In the event of an outage, a manual or Microsoft-managed failover promotes the secondary, yet even then writes go to one selected region, not multiple regions at once. Azure Files is a managed file share service, not a distributed database, so its replication model does not enable multi-region write capability and thus is unsuitable for the stated need.
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