AZ-305 Design data storage solutions Practice Question
A global company stores customer profile data in JSON format. The application requires low-latency writes and reads from multiple regions. The solution must support multi-region writes with automatic conflict resolution and provide high availability. Which Azure Cosmos DB configuration should they choose?
⚠ Common exam trap
Test-takers frequently assume strong consistency is required for data integrity, but Azure Cosmos DB enforces that multi-region writes only work with eventual consistency, and automatic conflict resolution handles the trade-off between consistency and availability.
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
✓
SQL API with eventual consistency and multi-region writes enabled
The scenario demands low-latency multi-region writes with automatic conflict resolution and high availability. Azure Cosmos DB's SQL API supports multi-region writes with eventual consistency, which is the only consistency level that allows multi-region writes. Eventual consistency provides the lowest latency and highest availability, and Cosmos DB's automatic conflict resolution handles concurrent writes across regions using last-writer-wins (LWW) or custom conflict resolution policies.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
SQL API with eventual consistency and multi-region writes enabled
Why this is correct
The SQL API natively stores JSON documents and supports multi-region writes as long as consistency is not set to strong or bounded staleness. Eventual consistency is the default and, along with session and consistent prefix, is compatible with an Azure Cosmos DB account configured for multiple write regions. When multiple write regions are used, Cosmos DB automatically resolves conflicts using last-writer-wins or a custom conflict resolution policy, making this a fully valid configuration.
- ✗
MongoDB API with strong consistency and multi-region writes enabled
Why it's wrong here
The MongoDB API in Cosmos DB does handle JSON-like documents, but strong consistency is incompatible with multi-region writes. Azure Cosmos DB only permits eventual, consistent prefix, and session consistency when the account has multiple write regions; strong consistency requires a single write region to guarantee linearizable reads and writes. Therefore, requesting strong consistency alongside multi-region writes is an invalid combination and would fail at account creation or configuration time.
- ✗
Table API with consistent prefix consistency and single-region writes
Why it's wrong here
The Table API is a key-value store, not a document database, so it lacks native JSON document querying and schema flexibility. Although consistent prefix consistency is a valid level and could be used with multi-region reads, the requirement explicitly calls for multi-region writes, and single-region writes cannot satisfy high availability or low-latency writes across regions. Thus this option fails both on the data model and the write replication requirement.
- ✗
Gremlin API with session consistency and multi-region writes enabled
Why it's wrong here
The Gremlin API is built for graph data models using vertices and edges, not for JSON document storage; storing customer profiles as JSON documents would be unnatural and require mapping every property to a graph structure. While session consistency is actually compatible with multi-region writes, the fundamental mismatch of the graph API to a document workload makes this option incorrect. The correct service for JSON documents is the SQL API, which is schema-agnostic and directly supports JSON.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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