DVA-C02 Troubleshooting and Optimization Practice Question
A developer is troubleshooting a slow Amazon DynamoDB table. The table has a read capacity of 1000 RCU and a write capacity of 500 WCU. The application frequently reads the same item. Which TWO actions can improve read performance?
⚠ Common exam trap
It's easy for candidates to choose to increase RCU (Option A) as a knee-jerk reaction to slow reads, overlooking that caching (DAX) and consistency model changes are more cost-effective and targeted solutions for repeated reads of the same item.
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
✓
Implement DynamoDB Accelerator (DAX) for caching.
DynamoDB Accelerator (DAX) is an in-memory cache that can reduce read latency for frequently accessed items from milliseconds to microseconds, offloading read traffic from the table and improving performance without requiring a capacity increase. Option E is correct because eventually consistent reads consume half the RCU of strongly consistent reads (0.5 RCU vs 1 RCU per 4 KB item) and return data faster, which is suitable when the application can tolerate slightly stale data for the same item.
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) to 2000.
Why it's wrong here
Increasing Read Capacity Units (RCU) primarily addresses throttling issues, where requests are rejected because the provisioned throughput is exceeded. If the table is merely 'slow' due to high latency per request rather than throttling, simply increasing RCU will not inherently reduce the individual request latency. It would only increase cost without improving the response time for each read operation.
- ✗
Add a Global Secondary Index (GSI) on the frequently read attribute.
Why it's wrong here
Adding a Global Secondary Index (GSI) allows for querying data using an alternate key, enabling new access patterns. However, it does not inherently speed up existing read operations on the base table's primary key. Furthermore, maintaining a GSI adds write overhead to the main table and can introduce eventual consistency considerations for queries against the index, potentially increasing overall complexity and not directly solving 'slow' reads on the primary key.
- ✗
Decrease the write capacity units (WCU) to 250.
Why it's wrong here
Decreasing Write Capacity Units (WCU) only impacts the rate at which data can be written to the DynamoDB table. This action has no direct or indirect effect on the performance, latency, or throughput of read operations. Read and write capacities are provisioned and consumed independently, meaning a change to WCU will not alleviate slow read performance.
- ✓
Implement DynamoDB Accelerator (DAX) for caching.
Why this is correct
DynamoDB Accelerator (DAX) is an in-memory cache specifically designed for DynamoDB, providing microsecond response times for read-heavy workloads. By caching frequently accessed items, DAX significantly reduces the latency of read operations and offloads read traffic from the underlying DynamoDB table. This direct caching mechanism is highly effective at improving application responsiveness for 'slow' reads.
- ✓
Use eventually consistent reads instead of strongly consistent reads.
Why this is correct
Using eventually consistent reads instead of strongly consistent reads offers a significant performance advantage. Eventually consistent reads consume half the Read Capacity Units (RCU) and typically return data with lower latency because they read from any replica, not necessarily the most up-to-date one. This trade-off of slight data staleness (usually within milliseconds) for improved speed and cost efficiency directly addresses the problem of 'slow' reads.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DVA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DVA-C02 exam.