DP-900 Practice Question: Describe considerations for working with non-relational data on Azure
This DP-900 practice question tests your understanding of describe considerations for working with non-relational data on azure. 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 travel booking application stores user itineraries in Azure Cosmos DB using the NoSQL API. Each itinerary document contains: UserID (unique to user), ItineraryID, Destination, BookingDate, and a nested array of Activities. The most common query is: 'Retrieve all itineraries for a specific UserID sorted by BookingDate descending.' To minimize Request Unit (RU) consumption, which partition key should be chosen?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Why wrong: Using ItineraryID would scatter each itinerary across partitions. A query for a user's itineraries would need to touch many partitions, increasing RU consumption.
B
UserID
UserID is the most common filter. All documents for one user are stored on the same partition, making the query single-partition and highly efficient.
C
Destination
Why wrong: Destination may lead to unbalanced partition sizes (e.g., 'Paris' having many documents) and queries by UserID would still be cross-partition if the user has multiple destinations.
D
BookingDate
Why wrong: BookingDate would likely cause hot partitions (e.g., today's date) and queries for a specific UserID would span multiple partitions, increasing RU.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
UserID
UserID is the correct partition key because the most common query filters on UserID, ensuring that all itineraries for a specific user are stored in the same physical partition. This allows the query to target a single partition, minimizing cross-partition queries and reducing Request Unit (RU) consumption. A partition key that aligns with the primary query filter is essential for optimal performance and cost efficiency in Azure Cosmos DB.
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.
✗
ItineraryID
Why it's wrong here
Using ItineraryID would scatter each itinerary across partitions. A query for a user's itineraries would need to touch many partitions, increasing RU consumption.
✓
UserID
Why this is correct
UserID is the most common filter. All documents for one user are stored on the same partition, making the query single-partition and highly efficient.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Destination
Why it's wrong here
Destination may lead to unbalanced partition sizes (e.g., 'Paris' having many documents) and queries by UserID would still be cross-partition if the user has multiple destinations.
✗
BookingDate
Why it's wrong here
BookingDate would likely cause hot partitions (e.g., today's date) and queries for a specific UserID would span multiple partitions, increasing RU.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose a unique identifier like ItineraryID as the partition key, thinking it ensures even distribution, but they overlook that the query pattern (filtering by UserID) requires the partition key to match the filter to avoid expensive cross-partition queries.
Detailed technical explanation
How to think about this question
Azure Cosmos DB uses the partition key to hash documents into logical partitions, each stored on a physical partition. When a query includes the partition key in the filter (e.g., WHERE UserID = '123'), the query engine routes the request directly to the partition containing that data, avoiding the RU overhead of cross-partition queries. In contrast, queries without the partition key in the filter must be fanned out to all partitions, with each partition consuming RUs for the scan, which can multiply costs significantly in large datasets.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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 considerations for working with non-relational data on Azure — This question tests Describe considerations for working with non-relational data on Azure — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: UserID — UserID is the correct partition key because the most common query filters on UserID, ensuring that all itineraries for a specific user are stored in the same physical partition. This allows the query to target a single partition, minimizing cross-partition queries and reducing Request Unit (RU) consumption. A partition key that aligns with the primary query filter is essential for optimal performance and cost efficiency in Azure Cosmos DB.
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: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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