The correct answer is distributed transaction coordination. This term precisely describes the difficulty of maintaining a rollback across two separate data stores with different consistency models—Azure SQL Database, which enforces strong ACID guarantees, and Azure Cosmos DB, which defaults to eventual consistency. The challenge lies in ensuring that when a transaction is aborted in the SQL database, the corresponding audit log entries in Cosmos DB are also removed within a short time frame, a constraint that requires custom orchestration (such as the saga or two-phase commit pattern) rather than native support. On the DP-900 exam, this scenario tests your understanding of the limitations of cross-service transactional consistency and the distinction between single-store ACID compliance and multi-store coordination. A common trap is to confuse this with simple eventual consistency or idempotency, but the key is recognizing that the requirement spans two distinct systems. Memory tip: think "two stores, one rollback" to remember that distributed transaction coordination is needed whenever you must keep separate databases in sync across a failure.
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 financial services company stores account balances in Azure SQL Database (strong consistency) and transaction audit logs in Azure Cosmos DB (eventual consistency by default). A compliance requirement demands that when a transaction is rolled back in the SQL database, the corresponding audit log entries in Cosmos DB must also be removed within a short time frame. Which term best describes the difficulty of maintaining this constraint?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Why wrong: Incorrect. ACID compliance applies to individual databases but cannot be enforced across unrelated stores without custom coordination.
B
Idempotency
Why wrong: Incorrect. Idempotency ensures repeated operations produce the same result but does not address cross-store transactional consistency.
C
Distributed transaction coordination
Correct. Managing atomicity across heterogeneous stores that lack native distributed transaction support requires custom compensation logic or a saga pattern.
D
Schema flexibility
Why wrong: Incorrect. Schema flexibility refers to the ability to handle varying data structures, not transactional consistency.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Distributed transaction coordination
Option C is correct because the scenario requires coordinating a rollback across two distinct data stores—Azure SQL Database (ACID-compliant, strong consistency) and Azure Cosmos DB (eventual consistency by default). This cross-system transactional consistency is a classic distributed transaction coordination problem, often addressed via patterns like the two-phase commit (2PC) or the saga pattern, but not natively supported between these two services without custom orchestration.
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.
✗
ACID compliance
Why it's wrong here
Incorrect. ACID compliance applies to individual databases but cannot be enforced across unrelated stores without custom coordination.
✗
Idempotency
Why it's wrong here
Incorrect. Idempotency ensures repeated operations produce the same result but does not address cross-store transactional consistency.
✓
Distributed transaction coordination
Why this is correct
Correct. Managing atomicity across heterogeneous stores that lack native distributed transaction support requires custom compensation logic or a saga pattern.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Schema flexibility
Why it's wrong here
Incorrect. Schema flexibility refers to the ability to handle varying data structures, not transactional consistency.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse ACID compliance (which is a property of a single database) with the ability to maintain atomicity across multiple independent data stores, leading them to select Option A instead of recognizing the need for distributed transaction coordination.
Detailed technical explanation
How to think about this question
Distributed transaction coordination across Azure SQL Database and Cosmos DB typically requires implementing a saga pattern or using a transaction coordinator like the .NET System.Transactions namespace with a two-phase commit protocol, though Cosmos DB does not natively support 2PC. In practice, developers often use compensating transactions (e.g., a separate rollback function that deletes the Cosmos DB log entry) to achieve eventual consistency, but this introduces a window where the constraint is not immediately satisfied, which is the core difficulty.
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 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.
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: Distributed transaction coordination — Option C is correct because the scenario requires coordinating a rollback across two distinct data stores—Azure SQL Database (ACID-compliant, strong consistency) and Azure Cosmos DB (eventual consistency by default). This cross-system transactional consistency is a classic distributed transaction coordination problem, often addressed via patterns like the two-phase commit (2PC) or the saga pattern, but not natively supported between these two services without custom orchestration.
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.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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