DP-900 Describe core data concepts Practice Question
A company wants to store JSON documents that need to be queried with high throughput and low latency globally. Which Azure data service is most appropriate?
⚠ Common exam trap
Test-takers frequently confuse Azure Table Storage's key-value model with JSON document support, or assume Azure SQL Database's JSON functions make it suitable for globally distributed, high-throughput JSON workloads, missing Cosmos DB's core differentiator of turnkey global distribution and guaranteed low latency.
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
Azure Cosmos DB is the most appropriate service because it is a globally distributed, multi-model database that natively supports JSON documents and provides guaranteed single-digit-millisecond latency at the 99th percentile, along with high throughput via configurable request units (RUs). Its turnkey global distribution enables low-latency reads and writes across multiple Azure regions, making it ideal for globally queried JSON workloads.
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
Why it's wrong here
Azure Table Storage is a NoSQL key-value store designed for massive semi-structured datasets, not for JSON document storage. While it can technically store JSON as an opaque string value, it does not provide native JSON querying capabilities such as indexing on nested properties or SQL-like JSON functions. Queries are limited to partition key and row key lookups, making it inefficient for content-based queries on JSON documents. Additionally, its latency is higher than Cosmos DB for global access patterns.
- ✓
Azure Cosmos DB
Why this is correct
Azure Cosmos DB is a fully managed NoSQL database explicitly built for JSON documents, offering native JSON support with automatic indexing of all properties. It provides guaranteed low latency (single-digit milliseconds) at any scale, coupled with turnkey global distribution across multiple Azure regions, enabling active-active configurations. Its SQL API allows rich querying over JSON documents using familiar syntax, and it supports multiple consistency models to balance performance and data correctness. This makes it the optimal choice for storing and querying JSON documents with global reach.
- ✗
Azure SQL Database
Why it's wrong here
Azure SQL Database is a relational database management system optimized for structured, schema-based data with ACID transactions. Although it offers some JSON functions (e.g., JSON_VALUE, OPENJSON), storing documents forces a rigid relational schema or a column with JSON text that is not as efficiently queryable as a native document store. It lacks Cosmos DB's native multi-region write capabilities and is not purpose-built for globally distributed document workloads. For a company needing to store and query JSON documents, SQL Database introduces unnecessary complexity and does not provide the same elastic scale for document data.
- ✗
Azure Blob Storage
Why it's wrong here
Azure Blob Storage is optimized for storing massive amounts of unstructured binary data, such as images, videos, and backups, not for querying object contents. A JSON document saved as a blob is treated as an opaque file; while you can retrieve the entire blob, you cannot run ad-hoc queries on its internal fields or properties without downloading and parsing it client-side. Azure Blob Storage lacks indexing and query engines for document data, making it unsuitable for applications that need frequent, targeted reads of JSON attribute values. It is a storage service, not a database service, and therefore fails the requirement for queryable JSON.
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Data Roles and Core Concepts
Key term
Azure Cosmos DB
Azure Cosmos DB is a fully managed, globally distributed NoSQL database service that offers fast reads and writes anywhere in the world with automatic scaling and multiple consistency models.
Key term
Service
A service is a software component or system that performs a specific function and is available to be used by other programs or users over a network.
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