AZ-305 Design data storage solutions Practice Question
A company is migrating a MongoDB-compatible application to Azure. The application requires low-latency reads and writes globally. It needs to support multi-region writes so that updates can be made from any region with automatic conflict resolution. The data is JSON documents that can vary in schema. The company wants a fully managed database service with native support for MongoDB APIs. Which Azure data service should they choose?
⚠ Common exam trap
It's easy for candidates to confuse 'Azure Database for MongoDB' (which does not exist) with Azure Cosmos DB's API for MongoDB, or incorrectly assume that a relational database like Azure SQL Database can handle schema-flexible JSON documents with global 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 with the API for MongoDB
Azure Cosmos DB with the API for MongoDB is the correct choice because it provides a fully managed, globally distributed database service that natively supports the MongoDB wire protocol. It offers multi-region writes with automatic conflict resolution using last-writer-wins (LWW) or custom conflict resolution policies, ensuring low-latency reads and writes globally. Its schema-agnostic nature handles JSON documents with varying schemas, meeting all stated requirements.
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
Why it's wrong here
Azure SQL Database is a fully managed relational database engine built on SQL Server technology. It uses a rigid schema and T-SQL for queries, offering no support for MongoDB's document-oriented BSON format or the MongoDB wire protocol. Consequently, a MongoDB-based application could not connect via its native drivers, and data modeling would require a complete redesign to relational tables.
- ✓
Azure Cosmos DB with the API for MongoDB
Why this is correct
Azure Cosmos DB with the API for MongoDB is a native implementation of the MongoDB wire protocol on a globally distributed, multi-model NoSQL database service. It enables existing MongoDB drivers to connect directly while gaining Cosmos DB's turnkey global distribution, multiple consistency levels, and SLA-backed performance. It supports both shared and dedicated throughput, and features like automatic indexing and conflict resolution for multi-region writes.
- ✗
Azure Database for MongoDB
Why it's wrong here
There is no Azure service formally named 'Azure Database for MongoDB' in the Azure product catalog. Azure's managed MongoDB-compatible offering is exclusively delivered through Azure Cosmos DB's API for MongoDB. Selecting this non-existent option indicates a misunderstanding of Azure's database portfolio and would lead to a failed or invalid architecture.
- ✗
Azure Cache for Redis
Why it's wrong here
Azure Cache for Redis is an in-memory key-value data store based on open-source Redis, optimized for low-latency caching and session state. It does not implement the MongoDB wire protocol, does not store documents in a queryable BSON format, and lacks multi-region write conflict resolution. While it can complement a NoSQL solution by caching hot data, it cannot serve as the primary persistent store for a MongoDB application.
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