Quick Answer
Azure Cosmos DB is the correct choice because it is a fully managed NoSQL database built to natively store and query JSON documents with a flexible schema, while guaranteeing single-digit millisecond read latencies at the 99th percentile for low-latency REST API access. Its SQL API automatically indexes every property in your JSON documents, enabling fast queries without requiring you to predefine or manage schemas. On the AZ-204 exam, this scenario tests your ability to distinguish Cosmos DB from alternatives like Azure Table Storage or SQL Database, which either lack native JSON support or cannot guarantee the same latency performance. A common trap is choosing Table Storage for its schema flexibility, but remember that Table Storage does not support native JSON document querying and has higher read latency. Memory tip: think “JSON + low latency = Cosmos DB,” and recall that Cosmos DB’s automatic indexing is what makes those fast, schema-agnostic reads possible.
This AZ-204 practice question tests your understanding of develop for azure storage. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You are developing a solution that needs to store and retrieve JSON documents with a flexible schema. The data is accessed via REST API and requires low-latency reads. Which Azure Storage service should you use?
Azure Blob Storage
Why wrong: Blob Storage is for binary files, not JSON document queries.
Azure Cosmos DB
Cosmos DB provides flexible schema and low-latency.
Azure Table Storage
Why wrong: Table Storage is key-value, not flexible schema.
Azure Files
Why wrong: Azure Files is for SMB file shares.
Answer choices
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 natively supports storing and querying JSON documents with a flexible schema via its SQL API, and it guarantees single-digit millisecond read latencies at the 99th percentile, which meets the low-latency requirement. Unlike other Azure storage services, Cosmos DB is a fully managed NoSQL database designed for REST API access with automatic indexing of all JSON properties.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Azure Blob Storage
Why it's wrong here
Blob Storage is for binary files, not JSON document queries.
Azure Cosmos DB
Why this is correct
Cosmos DB provides flexible schema and low-latency.
Related concept
Read the scenario before looking for a memorised answer.
Azure Table Storage
Why it's wrong here
Table Storage is key-value, not flexible schema.
Azure Files
Why it's wrong here
Azure Files is for SMB file shares.
Common exam traps
The trap here is that candidates often confuse Azure Blob Storage's ability to store JSON files (as blobs) with the ability to efficiently query and retrieve individual documents with low latency, overlooking the fact that Blob Storage lacks native indexing and querying capabilities for JSON content.
Detailed technical explanation
Azure Cosmos DB achieves low-latency reads through its indexing engine, which automatically indexes every property in a JSON document without requiring schema definitions, and it uses a multi-master replication model with tunable consistency levels. In practice, for a real-time application like a product catalog with varying attributes, Cosmos DB can serve point reads in under 10 ms by directly accessing documents via their unique resource ID, while Blob Storage would require downloading the entire blob and deserializing it, adding significant latency.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
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FAQ
Develop for Azure storage — This question tests Develop for Azure storage — Read the scenario before looking for a memorised answer..
The correct answer is: Azure Cosmos DB — Azure Cosmos DB is the correct choice because it natively supports storing and querying JSON documents with a flexible schema via its SQL API, and it guarantees single-digit millisecond read latencies at the 99th percentile, which meets the low-latency requirement. Unlike other Azure storage services, Cosmos DB is a fully managed NoSQL database designed for REST API access with automatic indexing of all JSON properties.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
About these practice questions
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Same concept, more angles
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. You need to store millions of small JSON documents (each less than 1 KB) that are accessed by key. The data is read-heavy and requires low-latency access. Which Azure storage solution should you use?
mediumWhy C: Azure Cosmos DB is the correct choice because it provides single-digit millisecond latency for point reads by key, supports automatic indexing of JSON documents, and offers a globally distributed, multi-model database service. For millions of small JSON documents accessed by key in a read-heavy workload, Cosmos DB's throughput-provisioned model and consistency levels optimize for low-latency access at scale.
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Last reviewed: Jun 24, 2026
This AZ-204 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the AZ-204 exam.
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