- A
PatientID
Correct. PatientID is the natural filter for the most common query, making it single-partition. It also has high cardinality, ensuring data is spread evenly across partitions.
- B
Timestamp
Why wrong: Incorrect. Using Timestamp as partition key would likely cause a hot partition because many documents with the same timestamp range would be written to the same logical partition, limiting throughput and performance.
- C
HeartRate
Why wrong: Incorrect. HeartRate is a measurement field with low cardinality (limited range of values), leading to large, unbalanced partitions and poor query performance.
- D
BloodPressure
Why wrong: Incorrect. BloodPressure, like HeartRate, has low cardinality and is not used in the most common query filter, making it a poor choice for partition key.
Quick Answer
The answer is PatientID. This property is the correct partition key for time-series data in Cosmos DB because the most common query filters by PatientID along with a time range, allowing the database to route the query to a single physical partition containing all documents for that patient, which minimizes cross-partition queries and reduces Request Unit (RU) consumption. On the Microsoft Azure Data Fundamentals DP-900 exam, this scenario tests your understanding of partition key selection for even data distribution and query efficiency—a common trap is choosing Timestamp, which would create a hot partition on the current time and force cross-partition queries for patient-specific lookups. Remember the memory tip: “Patient first, time second”—the partition key must match the primary filter in your most frequent query, not the range filter.
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 hospital stores patient vital signs data in Azure Cosmos DB. Each document contains PatientID, Timestamp, HeartRate, BloodPressure, and other measurements. The most common query retrieves all vital signs for a specific patient within a time range (e.g., last 24 hours). Which property should be chosen as the partition key to minimize Request Unit (RU) consumption and ensure even data distribution?
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.
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
PatientID
PatientID is the ideal partition key because the most common query filters by PatientID and a time range. With PatientID as the partition key, Cosmos DB can route the query to a single physical partition containing all documents for that patient, minimizing cross-partition queries and reducing RU consumption. It also ensures even data distribution since each patient generates a similar volume of vital signs data, avoiding hot partitions.
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.
- ✓
PatientID
Why this is correct
Correct. PatientID is the natural filter for the most common query, making it single-partition. It also has high cardinality, ensuring data is spread evenly across partitions.
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.
- ✗
Timestamp
Why it's wrong here
Incorrect. Using Timestamp as partition key would likely cause a hot partition because many documents with the same timestamp range would be written to the same logical partition, limiting throughput and performance.
- ✗
HeartRate
Why it's wrong here
Incorrect. HeartRate is a measurement field with low cardinality (limited range of values), leading to large, unbalanced partitions and poor query performance.
- ✗
BloodPressure
Why it's wrong here
Incorrect. BloodPressure, like HeartRate, has low cardinality and is not used in the most common query filter, making it a poor choice for partition key.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Microsoft often tests the misconception that Timestamp is a good partition key for time-based queries, but candidates fail to realize that Timestamp causes hot partitions and does not distribute write load evenly.
Detailed technical explanation
How to think about this question
Cosmos DB uses hash-based partitioning: the partition key value is hashed to determine the physical partition. For time-range queries, a common pattern is to use a composite key like PatientID + Timestamp, but since the exam focuses on a single property, PatientID alone is the best choice. In practice, if a single patient’s data exceeds 20 GB, you might need a synthetic partition key (e.g., PatientID + Date) to avoid the 20 GB per logical partition limit, but for the given scenario PatientID works.
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 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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Describe considerations for working with non-relational data on Azure — study guide chapter
Learn the concepts, then practise the questions
- →
Describe considerations for working with non-relational data on Azure practice questions
Targeted practice on this topic area only
- →
All DP-900 questions
982 questions across all exam domains
- →
Microsoft Azure Data Fundamentals DP-900 study guide
Full concept coverage aligned to exam objectives
- →
DP-900 practice test guide
How to use practice tests most effectively before exam day
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.
Describe core data concepts practice questions
Practise DP-900 questions linked to Describe core data concepts.
Describe an analytics workload on Azure practice questions
Practise DP-900 questions linked to Describe an analytics workload on Azure.
Identify considerations for relational data on Azure practice questions
Practise DP-900 questions linked to Identify considerations for relational data on Azure.
Describe considerations for working with non-relational data on Azure practice questions
Practise DP-900 questions linked to Describe considerations for working with non-relational data on Azure.
DP-900 fundamentals practice questions
Practise DP-900 questions linked to DP-900 fundamentals.
DP-900 scenario practice questions
Practise DP-900 questions linked to DP-900 scenario.
DP-900 troubleshooting practice questions
Practise DP-900 questions linked to DP-900 troubleshooting.
Practice this exam
Start a free DP-900 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this DP-900 question test?
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: PatientID — PatientID is the ideal partition key because the most common query filters by PatientID and a time range. With PatientID as the partition key, Cosmos DB can route the query to a single physical partition containing all documents for that patient, minimizing cross-partition queries and reducing RU consumption. It also ensures even data distribution since each patient generates a similar volume of vital signs data, avoiding hot partitions.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 30, 2026
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.