DEA-C01 Data Store Management Practice Question
A financial services company has an Amazon DynamoDB table named 'Transactions' with provisioned read capacity of 10,000 RCU and write capacity of 5,000 WCU. The table stores transaction records for the past 90 days. The application performs point reads by transaction ID (partition key) and range queries by customer ID and timestamp (GSI). Recently, the company started a new marketing campaign, causing a sudden spike in write traffic. The write capacity is now at 4,500 WCU, and the application is experiencing occasional throttling on writes. The data engineer needs to ensure that writes are not throttled during future campaigns, while keeping costs low. The table currently has auto scaling enabled with a maximum capacity of 10,000 WCU. Which solution should the engineer implement?
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 the table to DynamoDB on-demand capacity mode.
DynamoDB on-demand capacity mode automatically scales to accommodate traffic spikes, eliminating throttling without manual intervention and without fixed capacity limits, making it cost-effective for unpredictable traffic. Option B is wrong because DAX is a read cache and does not handle write throttling. Option C is wrong because using SQS adds latency and complexity; not ideal for real-time writes. Option D is wrong because increasing the maximum write capacity still has a limit and may not react quickly enough to sudden spikes, and may increase costs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Switch the table to DynamoDB on-demand capacity mode.
Why this is correct
DynamoDB on-demand capacity mode automatically scales to accommodate traffic spikes, eliminating throttling without manual intervention and without fixed capacity limits, making it cost-effective for unpredictable traffic.
- ✗
Use DynamoDB Accelerator (DAX) to cache write requests.
Why it's wrong here
DynamoDB Accelerator (DAX) is an in-memory cache for read operations only. It does not handle write requests, so it would not help with write throttling.
- ✗
Implement an Amazon SQS queue to buffer write requests and process them in batches.
Why it's wrong here
While an SQS queue can buffer write requests, it introduces additional latency and architectural complexity. It is not the simplest solution and may not be suitable for real-time write requirements.
- ✗
Increase the maximum write capacity in the auto scaling configuration to 20,000 WCU.
Why it's wrong here
Simply increasing the maximum auto scaling capacity to 20,000 WCU would increase costs unnecessarily and still may not react quickly enough to sudden spikes in traffic. On-demand capacity mode is a better solution for unpredictable workloads.
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Written by Johnson Ajibi, MSc IT Security
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