Azure Cosmos DB is the correct choice because it is the only Azure data service built specifically for storing and querying JSON documents with automatic indexing of every property. As a fully managed NoSQL database, Cosmos DB natively supports schema-free JSON documents, meaning any property you add is instantly indexed and queryable without manual configuration—perfect for scenarios where multiple services frequently update documents and need to search by any field. On the Microsoft Azure Data Fundamentals DP-900 exam, this question tests your understanding of when to use Cosmos DB versus other Azure data stores like Azure SQL Database or Azure Table Storage; a common trap is choosing Azure SQL Database because it can store JSON, but it lacks automatic indexing of all properties and is not optimized for high-frequency updates. Remember the key distinction: if the requirement is “JSON documents with automatic indexing on any property,” think Cosmos DB. A simple memory tip is “Cosmos covers all properties”—its indexing is automatic and comprehensive, just like the cosmos.
DP-900 Describe core data concepts Practice Question
This DP-900 practice question tests your understanding of describe core data concepts. 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.
A company needs to store JSON documents that are frequently updated by multiple services. The solution must support indexing and querying by any property. Which Azure data service should they use?
Why wrong: Azure Blob Storage stores unstructured blobs but does not provide indexing or querying by arbitrary properties without additional compute.
B
Azure SQL Database
Why wrong: Azure SQL Database is relational and requires a predefined schema; it does not natively support schema-less JSON documents with automatic indexing.
C
Azure Cosmos DB
Azure Cosmos DB is a globally distributed NoSQL database that stores JSON documents, automatically indexes all properties, and supports SQL-like queries.
D
Azure Table Storage
Why wrong: Azure Table Storage is a key-value store that requires a partition key and row key; it does not support querying by arbitrary properties.
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 a fully managed NoSQL database designed for JSON documents, offering native support for indexing every property automatically without requiring a predefined schema. Its multi-model API (including SQL API) allows querying by any property with low-latency reads and writes, making it ideal for services that frequently update JSON documents.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 Blob Storage
Why it's wrong here
Azure Blob Storage stores unstructured blobs but does not provide indexing or querying by arbitrary properties without additional compute.
✗
Azure SQL Database
Why it's wrong here
Azure SQL Database is relational and requires a predefined schema; it does not natively support schema-less JSON documents with automatic indexing.
✓
Azure Cosmos DB
Why this is correct
Azure Cosmos DB is a globally distributed NoSQL database that stores JSON documents, automatically indexes all properties, and supports SQL-like queries.
Related concept
Read the scenario before looking for a memorised answer.
✗
Azure Table Storage
Why it's wrong here
Azure Table Storage is a key-value store that requires a partition key and row key; it does not support querying by arbitrary properties.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse Azure Blob Storage's ability to store JSON files (as blobs) with the ability to query them by property, overlooking the lack of native indexing and querying capabilities.
Detailed technical explanation
How to think about this question
Azure Cosmos DB uses a schema-agnostic indexing engine that automatically indexes all properties in JSON documents, enabling efficient queries without manual index management. Its consistency levels (e.g., eventual, session, strong) allow tuning between performance and data freshness for multi-service updates. In a real-world scenario, an e-commerce platform with multiple microservices updating product inventory as JSON documents would benefit from Cosmos DB's automatic indexing and sub-10 ms read latencies at the 99th percentile.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this DP-900 question in full detail.
Describe core data concepts — This question tests Describe core data concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Azure Cosmos DB — Azure Cosmos DB is a fully managed NoSQL database designed for JSON documents, offering native support for indexing every property automatically without requiring a predefined schema. Its multi-model API (including SQL API) allows querying by any property with low-latency reads and writes, making it ideal for services that frequently update JSON documents.
What should I do if I get this DP-900 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This DP-900 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 DP-900 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.