Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A social media application stores user profiles in Azure Cosmos DB using the NoSQL API. Each profile includes UserID, Name, Email, and an array of Posts. The most common query retrieves a user's profile by UserID. The application requires strong consistency for writes so that once a profile is updated, all subsequent reads see the latest data. To minimize Request Unit (RU) consumption, which partition key should be chosen?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Best answer
UserID
UserID is unique and high cardinality, distributing data evenly. Retrieving by UserID becomes a point read, consuming the fewest RUs.
B
Distractor review
Email may not be unique and could lead to uneven distribution; queries by UserID would become cross-partition queries if Email is the partition key.
C
Distractor review
Name
Name is not unique and has low cardinality, causing hot partitions. Queries by UserID would be cross-partition.
D
Distractor review
A synthetic partition key combining UserID and Region
Adding Region to the partition key may improve distribution but would cause queries by UserID alone to be cross-partition, increasing RU consumption.
Common exam trap
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Technical deep dive
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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.
Related practice questions
Related DP-900 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
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FAQ
Questions learners often ask
What does this DP-900 question test?
Read the scenario before looking for a memorised answer.
What is the correct answer to this question?
The correct answer is: UserID — In Azure Cosmos DB, choosing a partition key with high cardinality and that evenly distributes data is crucial for performance and cost. For queries that retrieve a single document by a unique identifier, using that identifier as the partition key allows point reads, which consume minimal RUs. UserID is unique (high cardinality) and ensures even distribution. Using Email or Name may not be unique and could create hot partitions. A synthetic key combining UserID and Region may be unnecessary and could cause cross-partition queries if the query only uses UserID. Since the query is by UserID, the ideal partition key is UserID itself.
What should I do if I get this DP-900 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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