DP-900 Describe core data concepts Practice Question
A global social media application allows users to post updates and 'like' posts. The application is designed to prioritize availability and partition tolerance over strong consistency. As a result, when a user likes a post, the like count may not be immediately visible to all users, but it will eventually become consistent across all regions. Which consistency model does this application follow?
⚠ Common exam trap
Test-takers frequently confuse 'eventual consistency' with 'bounded staleness' because both allow stale reads, but eventual consistency has no guaranteed time or version bound, whereas bounded staleness imposes a strict limit—a distinction Microsoft explicitly tests in DP-900.
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
✓
Eventual consistency
The application prioritizes availability and partition tolerance, which aligns with the eventual consistency model. In this model, updates (like a 'like' count) are propagated asynchronously across replicas, and while reads may return stale data temporarily, all replicas will converge to the same value over time. This is typical of NoSQL systems like Apache Cassandra or Amazon DynamoDB when configured with eventual consistency.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Strong consistency
Why it's wrong here
Strong consistency ensures that any read operation returns the most recent write, but this comes at the cost of reduced availability and higher latency in distributed systems. The application explicitly prioritizes availability over strong consistency, so this is not the model used.
When this WOULD be correct
In a scenario where a banking application requires that a balance update is immediately visible to all subsequent read operations, even at the cost of reduced availability during network partitions, strong consistency would be the correct choice.
- ✓
Eventual consistency
Why this is correct
Eventual consistency guarantees that if no new updates are made, all replicas will eventually return the same value. This matches the scenario where updates are not immediately visible but become consistent over time, supporting high availability and partition tolerance.
- ✗
Consistent prefix
Why it's wrong here
Consistent prefix guarantees that reads always see a consistent prefix of the write history, meaning they never see partial writes out of order. While it provides some consistency, it does not guarantee eventual convergence of all writes in the way described.
When this WOULD be correct
A question asks: 'A messaging application requires that all users see messages in the exact order they were sent, even if some messages are delayed. Which consistency model ensures that reads never see out-of-order writes?' In that scenario, consistent prefix is correct.
- ✗
Bounded staleness
Why it's wrong here
Bounded staleness guarantees that reads will see writes within a specified time bound (e.g., 5 seconds). The scenario does not mention any time bound; it only says updates become consistent 'eventually', which aligns with eventual consistency rather than a bounded delay.
When this WOULD be correct
A financial trading application requires that all reads see writes within a guaranteed time window (e.g., 1 second) to prevent arbitrage, but can tolerate some delay. Bounded staleness would be correct here.
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.
✓Eventual consistencyCorrect answer▾
Why this is correct
Eventual consistency guarantees that if no new updates are made, all replicas will eventually return the same value. This matches the scenario where updates are not immediately visible but become consistent over time, supporting high availability and partition tolerance.
✗Strong consistencyWrong answer — click to see why▾
Why this is wrong here
The application prioritizes availability and partition tolerance over strong consistency, meaning it does not guarantee that all users see the same like count immediately. Strong consistency requires that all reads return the most recent write, which contradicts the eventual visibility described.
★ When this WOULD be the correct answer
In a scenario where a banking application requires that a balance update is immediately visible to all subsequent read operations, even at the cost of reduced availability during network partitions, strong consistency would be the correct choice.
Why candidates choose this
Candidates may confuse the need for accurate data (like counts) with strong consistency, not realizing that the application's design explicitly sacrifices immediate consistency for availability and partition tolerance.
✗Consistent prefixWrong answer — click to see why▾
Why this is wrong here
Consistent prefix guarantees that reads see writes in order, but does not guarantee that all replicas will eventually have the same value; it only ensures no gaps in the sequence. The question describes a system where updates propagate to all replicas over time, which is eventual consistency, not consistent prefix.
★ When this WOULD be the correct answer
A question asks: 'A messaging application requires that all users see messages in the exact order they were sent, even if some messages are delayed. Which consistency model ensures that reads never see out-of-order writes?' In that scenario, consistent prefix is correct.
Why candidates choose this
Candidates may confuse 'eventual' with 'prefix' because both involve delays, but consistent prefix focuses on ordering guarantees rather than convergence of all replicas to the same value.
✗Bounded stalenessWrong answer — click to see why▾
Why this is wrong here
Bounded staleness requires a bound on how stale data can be (e.g., within 5 seconds), but the question states no time bound, only eventual consistency across regions.
★ When this WOULD be the correct answer
A financial trading application requires that all reads see writes within a guaranteed time window (e.g., 1 second) to prevent arbitrage, but can tolerate some delay. Bounded staleness would be correct here.
Why candidates choose this
Candidates may confuse 'eventual' with 'bounded staleness' because both allow delays, but bounded staleness has a strict time limit, which is not mentioned in the question.
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?”
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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.