The correct answer is schema flexibility, paired with horizontal scalability as the second benefit. Azure Cosmos DB, as a NoSQL database, allows each record to have a different structure, meaning you can add or remove fields without altering a fixed schema—this is schema flexibility. Horizontal scalability, the other key benefit, means you can distribute data across multiple servers or regions by adding more partitions, enabling the database to handle massive workloads and low-latency access without downtime. On the DP-900 exam, this question tests your understanding of core NoSQL advantages versus relational databases; a common trap is confusing vertical scaling (adding power to a single server) with horizontal scaling. Remember the mnemonic “No Schema, No Single Server” to recall that NoSQL databases offer schema flexibility and scale out, not up.
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.
Which TWO are benefits of using a NoSQL database like Azure Cosmos DB? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Horizontal scalability
Azure Cosmos DB is a NoSQL database designed for horizontal scalability, which means it can distribute data across multiple servers and regions to handle massive workloads and low-latency access. This is achieved through partitioning and replication, allowing you to scale throughput and storage independently by adding more physical partitions or nodes.
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.
✗
Enforcing referential integrity
Why it's wrong here
Referential integrity is typically enforced in relational databases.
✗
Support for complex joins
Why it's wrong here
NoSQL databases generally do not support complex joins natively.
✓
Horizontal scalability
Why this is correct
NoSQL databases are designed to scale out across many nodes.
Related concept
Read the scenario before looking for a memorised answer.
✓
Schema flexibility
Why this is correct
NoSQL databases allow varying attributes per record.
Related concept
Read the scenario before looking for a memorised answer.
✗
Full ACID transactions across multiple documents
Why it's wrong here
ACID transactions are limited in scope in many NoSQL databases.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Microsoft often tests the misconception that NoSQL databases support full ACID transactions across multiple documents like relational databases, but in Cosmos DB, multi-document transactions are limited to the same logical partition and are not fully ACID across partitions.
Detailed technical explanation
How to think about this question
Cosmos DB uses a partition key to distribute data across physical partitions, enabling horizontal scale-out; each partition is a replicated unit with its own index and throughput. Schema flexibility is inherent because Cosmos DB is schema-agnostic—each item can have different attributes, and you can add new properties without migrations, which is critical for evolving applications like IoT or content management systems.
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: Horizontal scalability — Azure Cosmos DB is a NoSQL database designed for horizontal scalability, which means it can distribute data across multiple servers and regions to handle massive workloads and low-latency access. This is achieved through partitioning and replication, allowing you to scale throughput and storage independently by adding more physical partitions or nodes.
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.
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Question Discussion
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