AZ-305 Design data storage solutions Practice Question
A gaming company is developing a multiplayer online game that requires a low-latency data store for player profiles, inventory, and session state. The data is accessed globally, and the solution must support millions of concurrent players. The company expects write-heavy workloads with occasional reads. The solution must provide single-digit millisecond latency for reads and writes. The company also needs to run analytics on the data to understand player behavior, but analytics queries can tolerate higher latency (minutes). Which Azure data storage solution should the company recommend for the transactional data?
⚠ Common exam trap
Test-takers frequently choose Azure Redis Cache (Option B) because of its low latency, but they overlook that it is a cache, not a durable transactional store, and cannot serve as the primary data store for player profiles and inventory with global write-heavy workloads.
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 with multiple write regions
Azure Cosmos DB with multiple write regions is the correct choice because it provides global distribution with multi-master writes, delivering single-digit millisecond latency for both reads and writes at any scale. It supports millions of concurrent players via automatic and elastic scaling, and its change feed enables analytics with higher latency tolerance by streaming data to Azure Synapse or HDInsight without impacting transactional performance.
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 SQL Database with active geo-replication
Why it's wrong here
Azure SQL Database active geo-replication asynchronously replicates committed transactions to a readable secondary in a paired region, but the primary remains the sole write endpoint. All writes are applied to the primary first, and that single-region commit path cannot deliver the globally distributed, multi-master write performance this game needs. During a regional outage, failover is database-level and takes time, risking session continuity for players, and the synchronous/async replication trade-off does not match the required low-latency global writes.
- ✗
Azure Redis Cache with persistence
Why it's wrong here
Azure Redis Cache with persistence (RDB or AOF) is fundamentally a durable cache, not a transactional multi-region data store. It has a single primary node that accepts writes; writes are serialized to one region and replication to other regions is not a supported native multi-master topology. Persistence protects against restart data loss but does not provide the multi-region write consistency, conflict resolution, or distributed leader election required for a global multiplayer state store, so it fails the durability and global-write requirements.
- ✓
Azure Cosmos DB with multiple write regions
Why this is correct
Azure Cosmos DB with multiple write regions (multi-master) enables every region to accept writes, and each write is replicated asynchronously to all other regions with conflict resolution policies (e.g., last-writer-wins, custom). This delivers single-digit-millisecond read and write latencies at the 99th percentile anywhere in the world because the client can target the nearest region for both reads and writes. The service provides 99.999% availability with SLAs, automatic failover, and a choice of consistency levels, making it the correct fit for globally distributed, always-on multiplayer game state.
- ✗
Azure Table Storage with geo-redundancy
Why it's wrong here
Azure Table Storage is a schemaless NoSQL key-value store that supports geo-redundant storage (GRS) for durability, but failover to the secondary region is automatic only for the entire storage account and is not a multi-region write capability. Latency is not guaranteed to be single-digit milliseconds globally because Table Storage does not provide a managed multi-master model; writes go to the primary region and the secondary is only a read-only copy after failover. For a game requiring low-latency writes from players worldwide and active-active multi-region writes, Table Storage's eventual consistency and single-writer-region limitation are disqualifying.
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