The correct answer is to create a composite index on the filtered property. When you filter by a non-partition key in Azure Cosmos DB, queries without a composite index must fan out across all physical partitions, performing costly cross-partition scans. A composite index specifically targets the filtered property and the partition key together, allowing the query engine to efficiently route the request to only the relevant partitions, drastically reducing RU consumption and latency. On the DP-900 exam, this concept tests your understanding of how indexing strategies directly impact query performance, and a common trap is to assume that increasing Request Units (RUs) alone solves the problem—it does not fix the underlying indexing gap. Remember the memory tip: “Composite index on the filter, or your query will wander.”
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. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Your company uses Azure Cosmos DB with the Core (SQL) API. A collection contains millions of documents, and queries often filter by a property that is not the partition key. What should you do to improve query performance?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a composite index on the filtered property
Creating a composite index on the filtered property can improve query performance by avoiding cross-partition scans. However, if the property is not the partition key, queries may still need to fan out across partitions. Changing the partition key would require data migration. Increasing RU/s improves throughput but does not directly address the indexing issue. Enabling analytical store is for analytical queries, not operational.
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.
✓
Create a composite index on the filtered property
Why this is correct
Composite indexes can speed up queries on non-partition key properties, but cross-partition queries may still be needed.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the provisioned throughput (RU/s)
Why it's wrong here
Higher RU/s allows more operations per second but does not fix the indexing issue causing slow queries.
✗
Enable analytical store
Why it's wrong here
Analytical store is for running large analytical queries, not for improving point-read or filter query performance.
✗
Change the partition key to the filtered property
Why it's wrong here
Changing the partition key requires recreating the container and migrating data, which is disruptive.
Common exam traps
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.
Detailed technical explanation
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.
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.
Identify which DP-900 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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: Create a composite index on the filtered property — Creating a composite index on the filtered property can improve query performance by avoiding cross-partition scans. However, if the property is not the partition key, queries may still need to fan out across partitions. Changing the partition key would require data migration. Increasing RU/s improves throughput but does not directly address the indexing issue. Enabling analytical store is for analytical queries, not operational.
What should I do if I get this DP-900 question wrong?
Identify which DP-900 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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