Quick Answer
The answer is horizontal scaling across multiple regions and flexible schema. These two advantages are correct because NoSQL databases like Azure Cosmos DB are designed with a schema-agnostic architecture, allowing each document to have a different structure without requiring predefined table schemas or costly migrations, while also supporting seamless horizontal scaling by distributing data across multiple regions for low-latency global access. On the Microsoft Azure Data Fundamentals DP-900 exam, this question tests your understanding of the core differences between NoSQL and relational systems, often appearing as a multiple-select item where a common trap is confusing vertical scaling with horizontal scaling or assuming NoSQL lacks any schema enforcement. Remember the memory tip: NoSQL means "No Schema" and "Scale Out," whereas relational means "Rigid Schema" and "Scale Up."
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 advantages of using a NoSQL database like Azure Cosmos DB over a relational database like Azure SQL Database?
Support for complex joins
Why wrong: Relational databases are better for joins.
ACID transactions across multiple records
Why wrong: Relational databases are stronger in ACID.
Flexible schema design
NoSQL allows schema-less data models.
Horizontal scaling across multiple regions
NoSQL databases like Cosmos DB scale horizontally.
Enforced referential integrity
Why wrong: Relational databases enforce referential integrity.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Flexible schema design
Option C is correct because NoSQL databases like Azure Cosmos DB are schema-agnostic, allowing each document or item to have a different structure without requiring migrations or predefined table schemas. This flexibility is ideal for rapidly evolving applications or when ingesting heterogeneous data, whereas Azure SQL Database enforces a rigid schema that must be defined and altered explicitly.
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.
Support for complex joins
Why it's wrong here
Relational databases are better for joins.
ACID transactions across multiple records
Why it's wrong here
Relational databases are stronger in ACID.
Flexible schema design
Why this is correct
NoSQL allows schema-less data models.
Related concept
Read the scenario before looking for a memorised answer.
Horizontal scaling across multiple regions
Why this is correct
NoSQL databases like Cosmos DB scale horizontally.
Related concept
Read the scenario before looking for a memorised answer.
Enforced referential integrity
Why it's wrong here
Relational databases enforce referential integrity.
Common exam traps
The trap here is that candidates confuse the ACID support in NoSQL databases (which is limited to single-document operations) with the full multi-record ACID transactions of relational databases, leading them to incorrectly select Option B.
Detailed technical explanation
Under the hood, Cosmos DB uses a partition-key-based distribution model where each logical partition is an ACID-compliant transaction scope, but cross-partition transactions are not supported. This design enables horizontal scaling via automatic sharding across multiple regions, achieving single-digit-millisecond latencies at the 99th percentile. In contrast, Azure SQL Database relies on a fixed schema and vertical scaling, with global distribution requiring complex replication setups like active geo-replication.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
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FAQ
Describe core data concepts — This question tests Describe core data concepts — Read the scenario before looking for a memorised answer..
The correct answer is: Flexible schema design — Option C is correct because NoSQL databases like Azure Cosmos DB are schema-agnostic, allowing each document or item to have a different structure without requiring migrations or predefined table schemas. This flexibility is ideal for rapidly evolving applications or when ingesting heterogeneous data, whereas Azure SQL Database enforces a rigid schema that must be defined and altered explicitly.
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.
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Last reviewed: Jun 24, 2026
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