DP-900 Practice Question: Describe considerations for working with non-relational data on Azure
A company stores customer data in Azure Table Storage. They need to query by a combination of partition key (customer region) and row key (customer ID). Which query pattern is most efficient?
⚠ Common exam trap
The trap is thinking that PartitionKey alone is sufficient for efficiency, but the exam expects recognition that both keys are needed for the fastest point query.
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
✓
Query using both PartitionKey and RowKey
In Azure Table Storage, the most efficient query specifies both PartitionKey and RowKey because it targets a single entity directly. The PartitionKey determines the partition, and the RowKey uniquely identifies the entity within that partition. This point query is the fastest and most cost-effective, as it avoids scanning multiple partitions or entities.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Query using RowKey only
Why it's wrong here
Querying by RowKey alone is insufficient because RowKey is only unique within a partition, not across the entire table. Without a PartitionKey, Azure Table Storage cannot perform a point query and must scan every partition, merging results from all partitions. This cross-partition scan is significantly slower and consumes more request units and network bandwidth than a targeted lookup, making it an inefficient pattern for retrieving a specific entity.
- ✗
Scan all entities
Why it's wrong here
Scanning all entities is the most inefficient retrieval method because it reads every entity in the table, bypassing the partition/row key indexing mechanism entirely. This approach incurs maximum latency and throughput costs, and it scales poorly as the table grows. It should be reserved only for rare administrative tasks or very small tables, never for routine access to a single entity.
- ✓
Query using both PartitionKey and RowKey
Why this is correct
Querying with both PartitionKey and RowKey forms a point query that uniquely identifies a single entity, since their combination is the primary key of the table. The PartitionKey narrows the search to a specific partition, and the RowKey directly locates the entity within that partition's index. This is the most efficient, lowest-latency, and least costly operation Azure Table Storage supports for data retrieval.
- ✗
Query using PartitionKey only
Why it's wrong here
Querying by PartitionKey only returns every entity in the specified partition, not just the desired one. While this avoids a full table scan, it still requires enumerating and potentially filtering through potentially thousands of entities, which can be expensive. Because RowKey is not included, the result set is not guaranteed to be a single item, so additional client-side or query filtering is needed.
Go deeper
Related to this question
Learn chapter
Azure Table Storage and Blob Data
Key term
Partition key
A partition key is a value used by database systems to distribute data across multiple storage partitions, enabling faster queries and efficient scaling.
Key term
Table
A table is a structured collection of data organized into rows and columns, used in databases and spreadsheets to store and manage information efficiently.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Microsoft exam blueprint
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