DBS-C01 Management and Operations Practice Question
A company uses Amazon DynamoDB to store IoT sensor data. Each sensor writes a record every second. The table has a partition key of 'sensor_id' and a sort key of 'timestamp'. Over time, the team notices that write performance degrades for certain sensors that generate more data. The table uses provisioned capacity with auto scaling enabled. The application uses eventual consistency. The team needs to ensure consistent write performance without throttling. Which action should be taken?
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 partition key to include a random number or prefix to distribute writes evenly.
Adding a random number or prefix to the partition key distributes writes across multiple partitions, preventing hot partitions that cause throttling. Option B (increasing WCU) does not resolve the underlying hot partition issue, as each partition still has a maximum write capacity. Option C (on-demand mode) still has per-partition throughput limits and does not fix uneven write distribution. Option D (creating a GSI) does not affect the base table's write distribution; GSIs are for read efficiency, not write distribution.
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 partition key to include a random number or prefix to distribute writes evenly.
Why this is correct
Write sharding evens out the load across partitions, preventing any single partition from being overloaded.
- ✗
Increase the provisioned write capacity units (WCU) to a higher value.
Why it's wrong here
A single partition can only handle up to 1,000 WCU; increasing WCU does not bypass this limit.
- ✗
Switch the table to on-demand capacity mode.
Why it's wrong here
On-demand still has a per-partition throughput limit; hot partitions can still throttle.
- ✗
Create a global secondary index (GSI) with a different partition key to handle writes.
Why it's wrong here
GSI is for read access patterns; it does not affect the write distribution of the base table.
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