Question 114 of 1,663
DBS-C01 Workload-Specific Database Design Practice Question
A web application uses Amazon DynamoDB as its database. The application frequently queries items using a secondary index. The index's partition key has high cardinality, but the query latency is higher than expected. Which action would MOST likely improve query performance?
⚠ Common exam trap
Test-takers frequently assume high cardinality automatically guarantees good performance, overlooking that the GSI's provisioned read capacity is a separate resource that must be scaled independently to avoid throttling.
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
✓
Increase the read capacity units (RCU) for the global secondary index.
A Global Secondary Index (GSI) has its own provisioned read capacity, separate from the base table. If the GSI's read capacity units (RCU) are insufficient to handle the query workload, requests may be throttled, leading to higher latency. Increasing the RCU for the GSI directly addresses this bottleneck by allowing more concurrent read operations against the index.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use a Scan operation instead of Query to retrieve items from the index.
Why it's wrong here
Scan is less efficient and consumes more throughput than Query.
- ✗
Add additional sort key attributes to the index to better distribute the data.
Why it's wrong here
The index already has high cardinality; adding sort keys may not help and could increase costs.
- ✗
Convert the global secondary index to a local secondary index.
Why it's wrong here
Local secondary index shares throughput with the table, not improving latency if table is not throttled.
- ✓
Increase the read capacity units (RCU) for the global secondary index.
Why this is correct
Insufficient read capacity on the index can cause throttling and higher latency.
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Last reviewed: Jul 4, 2026
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