DBS-C01 Workload-Specific Database Design Practice Question
A media company stores video metadata in Amazon DynamoDB. The table has partition key 'video_id' and sort key 'upload_date'. The application frequently queries videos by 'category' and 'status'. The access pattern changes over time. Which design minimizes cost and maximizes query flexibility?
⚠ Common exam trap
The DBS-C01 exam often tests the misconception that a single GSI with a composite sort key can replace multiple GSIs, but the trap here is that a GSI's partition key determines the primary query dimension, and using a single GSI with 'category' as partition key cannot efficiently serve queries that filter only by 'status' without a full scan of that GSI.
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
✓
Create multiple GSIs with different partition keys to support various query patterns
Creating multiple GSIs with different partition keys allows the application to support various query patterns (e.g., by category, by status, or combined) without incurring the cost of scanning the base table. DynamoDB charges for read/write capacity and storage per GSI, so multiple GSIs are cost-effective only if each serves a distinct access pattern, and this design maximizes query flexibility by enabling efficient key-based lookups for changing workloads.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create a single GSI with partition key 'category' and sort key 'status'
Why it's wrong here
A single GSI can't cover all future query patterns.
- ✓
Create multiple GSIs with different partition keys to support various query patterns
Why this is correct
Multiple GSIs provide query flexibility at the cost of additional storage, but DynamoDB allows up to 20 GSIs.
- ✗
Use DynamoDB Streams to replicate data to Amazon Elasticsearch Service
Why it's wrong here
Adds operational complexity and cost; may be overkill for simple queries.
- ✗
Redesign to a single DynamoDB table that aggregates all attributes into the partition key
Why it's wrong here
Single table design may not support all queries efficiently.
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