DBS-C01 Workload-Specific Database Design Practice Question
A gaming company runs a global leaderboard on Amazon DynamoDB. The leaderboard is updated frequently and must return the top 100 scores in milliseconds. The current design uses a single table with a Global Secondary Index (GSI) on score. However, the query to retrieve top scores often throttles under load. Which design change would best improve performance?
⚠ Common exam trap
Test-takers frequently assume caching (DAX) or consistency changes will fix throttling, but the real issue is write-side hot partitions, which the write shard pattern directly addresses by distributing the write load.
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 a write shard pattern using a random suffix on the partition key and a GSI on score.
The write shard pattern distributes high-frequency writes across multiple partition keys by appending a random suffix, preventing hot partitions. The GSI on score still allows efficient top-N queries by scanning the index in descending order. This avoids throttling by spreading write capacity evenly, while the GSI remains a sparse index that can be queried without impacting the base table's write throughput.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use a scan operation with a filter to retrieve top scores.
Why it's wrong here
Scan is inefficient for large datasets and does not guarantee top scores without sorting.
- ✓
Implement a write shard pattern using a random suffix on the partition key and a GSI on score.
Why this is correct
Sharding distributes write load, and the GSI on score enables efficient range queries for top scores.
- ✗
Add DynamoDB Accelerator (DAX) in front of the table.
Why it's wrong here
DAX caches reads but does not reduce write throttling on the GSI.
- ✗
Switch to strongly consistent reads for the leaderboard query.
Why it's wrong here
Consistency model does not affect throttling.
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