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DP-900 Practice Question: Describe considerations for working with non-relational data on Azure

A social media application stores user profile data as JSON documents. Each user's document has a different structure, with fields that vary based on user activity. The application needs to query these documents efficiently using SQL-like syntax and support high write throughput. Which Azure data store is most appropriate for this workload?

⚠ Common exam trap

It's easy for candidates to confuse Azure Table Storage's key-value capabilities with document database features, overlooking that Table Storage does not support JSON documents, nested fields, or SQL-like queries, whereas Cosmos DB is explicitly designed for such 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

Azure Cosmos DB is the most appropriate choice because it natively supports storing and querying JSON documents with varying schemas, offers SQL-like query syntax via its core (SQL) API, and provides guaranteed low-latency reads/writes at any scale with automatic indexing of all fields. Its multi-model nature and configurable consistency levels make it ideal for high-throughput workloads like a social media application.

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 relational database that enforces a fixed schema, so storing user profiles with highly variable JSON structures would require either creating a wide table with many nullable columns or storing the JSON as a string and parsing it with functions like JSON_VALUE and OPENJSON. This approach loses the benefits of native relational indexing and constraints for the JSON content, and significant schema variations would necessitate constant migrations or complex query logic. It is a valid choice for hybrid relational/JSON scenarios but is not optimized for purely variable document-centric data.

    When this WOULD be correct

    If the question required ACID transactions, complex joins, and a fixed schema for user profile data, Azure SQL Database would be appropriate.

  • Azure Blob Storage

    Why it's wrong here

    Azure Blob Storage is an object storage service for unstructured binary files such as images, videos, and backups. Although you can save a JSON file to a blob, the service does not index, parse, or query the JSON content server-side; retrieving and filtering a specific user profile would require downloading the entire blob and deserializing it in your application. Its intended use case is static file storage, not serving as a document database with flexible schema and built-in querying.

    When this WOULD be correct

    A question requiring storage of massive binary files (e.g., user-uploaded photos or videos) with high scalability and low cost, where querying is done via metadata or separate indexing, would make Azure Blob Storage the correct answer.

  • Azure Cosmos DB

    Why this is correct

    Azure Cosmos DB is a globally distributed, multi-model NoSQL database that natively stores JSON documents as first-class citizens. Its flexible schema allows user profiles with varying fields and nested structures to be inserted without migrations, while the SQL API provides rich, index-backed querying over nested JSON properties. With turnkey global distribution, tunable consistency, and guaranteed low-latency reads/writes, it is explicitly designed for social media workloads that demand both variable data shapes and high throughput at scale.

  • Azure Table Storage

    Why it's wrong here

    Azure Table Storage is a NoSQL key-value store that partitions entities by partition key and row key, supporting property-based queries on up to 252 typed columns. It cannot represent deeply nested JSON hierarchies; you would have to serialize the entire profile into a single string property, which makes querying inside the document impossible without client‑side deserialization of every scanned entity. Its fixed entity model and lack of native document indexing make it unsuitable for the flexible, nested JSON profiles described in this scenario.

    When this WOULD be correct

    A question requiring a cost-effective, schema-less NoSQL store for high-volume, low-latency access to simple key-value data (e.g., storing device settings or session state) where SQL queries and complex document structures are not needed.

Option-by-option analysis

Why each answer is right or wrong

Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The DP-900 exam frequently reuses these exact scenarios with slightly different constraints.

Azure Cosmos DBCorrect answer

Why this is correct

Azure Cosmos DB is a globally distributed, multi-model NoSQL database that natively stores JSON documents as first-class citizens. Its flexible schema allows user profiles with varying fields and nested structures to be inserted without migrations, while the SQL API provides rich, index-backed querying over nested JSON properties. With turnkey global distribution, tunable consistency, and guaranteed low-latency reads/writes, it is explicitly designed for social media workloads that demand both variable data shapes and high throughput at scale.

Azure SQL DatabaseWrong answer — click to see why

Why this is wrong here

Azure SQL Database requires a fixed relational schema, but the question specifies JSON documents with varying structures, making it unsuitable for schema-less data.

★ When this WOULD be the correct answer

If the question required ACID transactions, complex joins, and a fixed schema for user profile data, Azure SQL Database would be appropriate.

Why candidates choose this

Candidates may assume SQL-like querying implies a relational database, overlooking that Cosmos DB also supports SQL syntax for JSON documents.

Azure Blob StorageWrong answer — click to see why

Why this is wrong here

Azure Blob Storage is optimized for storing large unstructured binary data (e.g., images, videos) and does not natively support SQL-like querying of JSON documents or high write throughput for document-level operations.

★ When this WOULD be the correct answer

A question requiring storage of massive binary files (e.g., user-uploaded photos or videos) with high scalability and low cost, where querying is done via metadata or separate indexing, would make Azure Blob Storage the correct answer.

Why candidates choose this

Candidates may confuse JSON documents with unstructured data, assuming Blob Storage's support for JSON files is sufficient, and overlook its lack of native querying and transaction support for document databases.

Azure Table StorageWrong answer — click to see why

Why this is wrong here

Azure Table Storage does not support SQL-like querying or JSON document storage; it is a NoSQL key-value store for structured, non-relational data with a fixed schema per partition.

★ When this WOULD be the correct answer

A question requiring a cost-effective, schema-less NoSQL store for high-volume, low-latency access to simple key-value data (e.g., storing device settings or session state) where SQL queries and complex document structures are not needed.

Why candidates choose this

Candidates may confuse Azure Table Storage with a document database because both are NoSQL, but they overlook that Table Storage lacks JSON document support and SQL query capabilities.

Analysis generated from the official DP-900blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”

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Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

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