Question 436 of 724
DVA-C02 Global Secondary Index (GSI) Practice Question
A developer is troubleshooting performance issues in an application that uses Amazon DynamoDB as the primary data store. The application reads a large set of items using a Query operation on a Global Secondary Index (GSI). The developer notices high read latency and throttled requests on the GSI. The base table has sufficient read capacity. The GSI is projected with KEYS_ONLY. Which action would most likely reduce the latency and throttling?
⚠ Common exam trap
Many candidates assume increasing the base table's capacity will resolve all read performance issues, failing to recognize that GSIs have independent capacity allocations and that throttling on a GSI requires adjusting the index's RCU, not the base table's.
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) of the GSI.
A Global Secondary Index (GSI) has its own provisioned read capacity, separate from the base table. When a Query operation reads from a GSI, it consumes RCUs from the GSI's capacity, not the base table's. Since the base table has sufficient read capacity but the GSI is experiencing throttling and high latency, increasing the GSI's RCU directly addresses the bottleneck by allowing more read requests per second 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.
- ✗
Increase the read capacity units (RCU) of the base table.
Why it's wrong here
Increasing the read capacity units (RCU) of the base table will not resolve throttling on a Global Secondary Index (GSI). GSIs maintain their own independent provisioned throughput capacity, separate from the base table. Throttling on a GSI specifically indicates that its dedicated RCU limit has been exceeded, meaning adjustments to the base table's capacity would have no impact on the GSI's ability to handle read requests.
- ✗
Change the GSI projection to ALL.
Why it's wrong here
Changing the GSI projection to ALL copies all attributes from the base table item into the GSI. While this can potentially reduce the need for subsequent `GetItem` calls to the base table by making more data available directly in the index, it does not increase the GSI's provisioned read capacity. The GSI would still experience throttling if the volume of read requests exceeds its allocated RCU, regardless of the number of attributes it contains.
- ✓
Increase the read capacity units (RCU) of the GSI.
Why this is correct
Throttling on a Global Secondary Index (GSI) is a direct indication that its provisioned read capacity units (RCU) are insufficient to handle the current read request volume. Since GSIs have their own distinct capacity settings, increasing the RCU specifically for the GSI directly addresses this bottleneck. This action allows the index to process more read operations per second, thereby alleviating throttling and improving application performance and latency.
- ✗
Create a Local Secondary Index instead.
Why it's wrong here
A Local Secondary Index shares the read capacity of the base table, which is already sufficient. However, it does not support queries across multiple partition keys as a GSI does, and may not solve the throttling issue.
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Last reviewed: Jun 11, 2026
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