DEA-C01 Data Store Management Practice Question
A startup is building a ride-sharing application that uses Amazon DynamoDB to store trip data. The table has a partition key of 'trip_id' and a sort key of 'status'. The application writes a new item when a trip starts and updates the status when the trip ends. The development team is experiencing high write latency during peak hours. The table is provisioned with 5,000 write capacity units (WCU) and 5,000 read capacity units (RCU). CloudWatch metrics show that WriteThrottleEvents are occurring frequently, but the consumed write capacity is never above 4,000 WCU. The team suspects that the issue is due to hot partitions. How should the data engineer resolve this issue?
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
✓
Modify the application to add a random suffix to the partition key when writing items.
Adding a random suffix to the partition key distributes writes across multiple partitions, preventing any single partition from becoming a hot spot and causing throttling. Option B is incorrect because DAX is an in-memory cache that speeds up reads, not writes; it does not address write throttling. Option C is incorrect because decreasing RCU does not affect write performance; write throttling is independent of read capacity. Option D is incorrect because increasing WCU does not solve hot partition issues; throttling occurs at the partition level, and a single partition can only handle up to 1000 WCU per partition. Thus, distributing writes is the appropriate solution.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Modify the application to add a random suffix to the partition key when writing items.
Why this is correct
Adding random suffix distributes writes across multiple partitions, reducing hot spots.
- ✗
Enable DynamoDB Accelerator (DAX) to cache write operations.
Why it's wrong here
DAX caches reads, not writes.
- ✗
Decrease the provisioned RCU to 2,000 to reduce costs.
Why it's wrong here
Reducing RCU does not affect write throttling.
- ✗
Increase the provisioned WCU to 10,000 to handle the spikes.
Why it's wrong here
Increasing WCU does not alleviate hot partition issues; throttling occurs per partition.
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