Describe considerations for working with non-relational data on Azure →hardMultiple ChoiceObjective-mapped
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?
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
Table Storage is optimized for point queries using both PartitionKey and RowKey. Using both keys allows direct access to the entity without scanning. Filtering only by RowKey across partitions results in a full table scan. Using only PartitionKey retrieves all rows in that partition, which is less efficient. Scanning all entities is the worst.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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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.
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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.
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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.
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Related to this question
Learn chapter
Data Roles and Core Concepts
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.
Key term
Data
Data is raw, unprocessed information, like numbers, words, or measurements, that can be stored, processed, and analyzed by computers.
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