DP-900 Describe core data concepts Practice Question
An e-commerce application processes customer orders. When an order is placed, the system must decrement the inventory count and process the payment. The application ensures that either both operations complete successfully or both are rolled back if any error occurs. Which database property does this guarantee?
⚠ Common exam trap
It's easy for candidates to confuse atomicity with consistency, thinking that 'keeping data valid' is the same as 'all-or-nothing execution,' but atomicity is specifically about the transaction's indivisibility, not about data integrity rules.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Atomicity
Atomicity ensures that a transaction is treated as a single, indivisible unit of work: either all operations within it (decrement inventory and process payment) complete successfully, or none are applied. If any part fails, the database rolls back all changes, maintaining the 'all-or-nothing' guarantee. This is the core property described in the scenario.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Atomicity
Why this is correct
Atomicity is the ACID property that treats a transaction as a single, indivisible unit of work. If any statement within the transaction (such as updating inventory or recording the order) fails, the entire transaction is rolled back, leaving the database exactly as it was before the transaction began. This all-or-nothing behavior prevents partial updates, ensuring that a customer order is either fully recorded or not recorded at all.
- ✗
Consistency
Why it's wrong here
Consistency is the ACID property that ensures a transaction transforms the database from one valid state to another, preserving all defined rules such as constraints, triggers, and foreign keys. If an order would violate a business rule or integrity constraint, consistency would prevent that final state, but it does not guarantee that a failure mid-transaction rolls back the whole unit. Consistency is about the correctness of the resulting data state, not the indivisibility of the transaction's execution, making it incorrect for this scenario.
When this WOULD be correct
A question that asks: 'A database constraint ensures that after an order is placed, the total inventory count across all warehouses remains non-negative. Which property does this enforce?' would make consistency the correct answer, as it maintains data integrity rules.
- ✗
Isolation
Why it's wrong here
Isolation is the ACID property that governs how concurrent transactions interact with each other, preventing them from seeing each other's uncommitted changes or otherwise interfering. It deals with the visibility of intermediate states across multiple simultaneously running transactions, using mechanisms like row locks or multiversion concurrency control. It says nothing about whether a single transaction itself is atomic, so it does not address the all-or-nothing requirement of an order processing operation.
When this WOULD be correct
If the question described two concurrent transactions, such as one updating inventory and another reading inventory, and the system must prevent the read from seeing an intermediate state, then Isolation would be the correct property.
- ✗
Durability
Why it's wrong here
Durability is a different ACID property that guarantees that once a transaction has been committed, its changes are permanently persisted in the database, even if a system crash, power loss, or other failure occurs immediately afterward. It does not concern itself with how a transaction executes or rolls back on failure; rather, it ensures that committed data survives any subsequent failure. Therefore, durability cannot explain why a partially failed order transaction would be undone, so it is not the correct answer.
When this WOULD be correct
A question asks: 'After a successful order transaction, the system crashes. The database guarantees that the order and inventory updates are not lost. Which property ensures this?' The correct answer would be Durability.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The DP-900 exam frequently reuses these exact scenarios with slightly different constraints.
✓AtomicityCorrect answer▾
Why this is correct
Atomicity is the ACID property that treats a transaction as a single, indivisible unit of work. If any statement within the transaction (such as updating inventory or recording the order) fails, the entire transaction is rolled back, leaving the database exactly as it was before the transaction began. This all-or-nothing behavior prevents partial updates, ensuring that a customer order is either fully recorded or not recorded at all.
✗ConsistencyWrong answer — click to see why▾
Why this is wrong here
Consistency ensures that a transaction transforms the database from one valid state to another, but the question specifically describes the 'all-or-nothing' execution of multiple operations, which is the definition of atomicity, not consistency.
★ When this WOULD be the correct answer
A question that asks: 'A database constraint ensures that after an order is placed, the total inventory count across all warehouses remains non-negative. Which property does this enforce?' would make consistency the correct answer, as it maintains data integrity rules.
Why candidates choose this
Candidates may confuse atomicity with consistency because both are ACID properties related to transaction correctness, and the scenario of ensuring both operations succeed or fail together might be misconstrued as maintaining data consistency.
✗IsolationWrong answer — click to see why▾
Why this is wrong here
Isolation ensures concurrent transactions do not interfere, but the question describes a single transaction that must complete entirely or not at all, which is Atomicity, not Isolation.
★ When this WOULD be the correct answer
If the question described two concurrent transactions, such as one updating inventory and another reading inventory, and the system must prevent the read from seeing an intermediate state, then Isolation would be the correct property.
Why candidates choose this
Candidates may confuse the 'all or nothing' requirement with the idea of isolating operations from each other, or they may think that ensuring both operations complete without interference relates to Isolation.
✗DurabilityWrong answer — click to see why▾
Why this is wrong here
Durability ensures that once a transaction is committed, its changes persist even after a system failure. The question describes a scenario where operations are rolled back on error, which is about atomicity (all-or-nothing), not durability.
★ When this WOULD be the correct answer
A question asks: 'After a successful order transaction, the system crashes. The database guarantees that the order and inventory updates are not lost. Which property ensures this?' The correct answer would be Durability.
Why candidates choose this
Candidates may confuse durability with atomicity because both involve transaction reliability, but durability focuses on persistence after commit, not the all-or-nothing execution during the transaction.
Analysis generated from the official DP-900blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Go deeper
Related to this question
About these practice questions
One of 820 original DP-900 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.