Question 840 of 1,663
DBS-C01 Monitoring and Troubleshooting Practice Question
An application using Amazon DynamoDB is experiencing higher than expected read costs. The table uses on-demand capacity mode. The read pattern is mostly fetching small items (1 KB) using GetItem. Which of the following is the most cost-effective optimization?
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
✓
Switch to eventually consistent reads for GetItem operations
The most cost-effective because eventually consistent reads consume half the read capacity units (0.5 RCU for items up to 4 KB) compared to strongly consistent reads (1 RCU). Since items are small (1 KB) and the table uses on-demand capacity, halving RCU consumption directly reduces read costs. Option A: Switching to provisioned capacity with auto scaling adds complexity and may not reduce costs if traffic is unpredictable; on-demand is already suitable for variable workloads. Option B: Application-level compression would not significantly reduce RCU consumption because items are already under the 4 KB RCU threshold. Option C: Adding DAX introduces additional cost and primarily improves latency, not read cost, as DAX still charges for reads from DynamoDB.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Change the table to provisioned capacity mode with auto scaling
Why it's wrong here
On-demand is already cost-effective for unpredictable traffic; provisioned may not save money.
- ✗
Compress the items using application-level compression
Why it's wrong here
Compression is not supported by DynamoDB; items are stored as-is.
- ✗
Use DAX to cache the read results
Why it's wrong here
DAX adds cost and does not reduce RCU consumption for cached reads.
- ✓
Switch to eventually consistent reads for GetItem operations
Why this is correct
Eventually consistent reads consume half the RCU of strongly consistent reads.
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Last reviewed: Jun 20, 2026
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