DBS-C01 Management and Operations Practice Question
A company is using Amazon DynamoDB for a gaming leaderboard. The table has a partition key of 'game_id' and a sort key of 'score'. The application performs a query to retrieve the top 10 scores for a given game_id. The query uses ScanIndexForward: false and Limit: 10. Recently, the query response time has increased. The table's read capacity is 1000 RCU, and the average item size is 1 KB. Which is the most likely cause of the increased latency?
⚠ Common exam trap
Many exam-takers assume increased latency is due to insufficient total provisioned capacity (Option C) or a missing index (Option A), but the real issue is uneven workload distribution causing a hot partition, which is a common DynamoDB performance pitfall.
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
✓
A hot partition on the game_id key is causing throttling for that specific partition.
The increased latency is most likely due to a hot partition on the 'game_id' key. When a specific game_id receives a disproportionate amount of write or read traffic, that single partition can exceed its throughput limits (1/1000th of provisioned RCU per partition), causing throttling and retries that degrade query response time. Even though the query uses ScanIndexForward: false and Limit: 10, the request is still constrained by the partition's capacity, and throttling at the partition level leads to increased latency.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The table lacks a global secondary index on game_id, causing a full table scan.
Why it's wrong here
The table already has game_id as partition key, so queries by game_id are efficient without a GSI.
- ✗
The query is using strongly consistent reads instead of eventually consistent reads.
Why it's wrong here
Strongly consistent reads consume twice the RCU but are not the default; the query uses eventually consistent reads unless specified.
- ✗
The provisioned read capacity is too low for the query pattern.
Why it's wrong here
1000 RCU is sufficient for 10 items of 1 KB each; the query consumes only a few RCUs.
- ✓
A hot partition on the game_id key is causing throttling for that specific partition.
Why this is correct
Even if total RCU is adequate, a single partition can exceed its throughput share, causing throttling and increased latency.
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Written by Johnson Ajibi, MSc IT Security
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