DP-900 Describe core data concepts Practice Question
A company needs to store JSON documents that require flexible schema and low-latency access globally. Which Azure data service should they use?
⚠ Common exam trap
It's easy for candidates to confuse Azure Blob Storage's ability to store JSON files as blobs with the need for a database that can query and index JSON documents with low-latency global access, leading them to incorrectly choose Blob Storage instead of Cosmos DB.
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 correct choice because it is a globally distributed, multi-model database service that natively supports JSON documents with flexible schema. It offers turnkey global distribution, single-digit-millisecond latency at the 99th percentile, and multiple consistency models, making it ideal for low-latency access worldwide.
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
While Azure Table Storage is a NoSQL key-value store that can tolerate entities with different properties, it does not natively index or query nested JSON fields. Its primary access pattern is by partition key and row key, so flexible queries on the contents of a JSON document are limited and inefficient. In addition, although Azure Storage offers geo-redundancy, Azure Table Storage does not provide the turnkey multi-region write and tunable consistency model needed for a globally distributed document database. Thus, it fails both the document querying and global distribution requirements.
- ✗
Azure SQL Database
Why it's wrong here
Azure SQL Database is a relational database management system that requires a fixed, predefined schema of tables, columns, and data types. You can store JSON text in a column, and recent versions include functions like JSON_VALUE and OPENJSON, but every document must still conform to the table's columns or be hidden in a string, and schema changes require migrations. The flexible schema requirement—where each document can have its own unique fields—is fundamentally at odds with a relational model, making it the wrong choice for this scenario.
- ✗
Azure Blob Storage
Why it's wrong here
Azure Blob Storage is an object storage service meant for unstructured data such as files, images, and backups, not for interactive document databases. While you can upload a JSON file as a blob, there is no built-in query engine or index that lets you retrieve a subset of documents based on their JSON content—you would have to download and parse each blob in your application. It also lacks native global distribution with multiple write regions and consistency levels, so for a flexible JSON document store with querying needs, Blob Storage is clearly insufficient.
- ✓
Azure Cosmos DB
Why this is correct
Azure Cosmos DB is a multi-model NoSQL database that natively stores JSON documents and automatically indexes every property without requiring a schema. Its Core (SQL) API provides a SQL-like query language that can filter, project, and join over nested JSON structures, enabling flexible document access. Additionally, Cosmos DB offers turnkey global distribution across Azure regions, with multiple consistency levels and support for multi-region writes, ensuring low-latency data access for users anywhere. This combination of schema-agnostic JSON handling and global distribution exactly matches the company's stated needs.
Go deeper
Related to this question
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Data Roles and Core Concepts
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.
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.
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