DBS-C01 Workload-Specific Database Design Practice Question
A company uses Amazon DynamoDB to store user profiles. The access pattern is mostly GetItem by user_id. They want to reduce costs. Which design change is most effective?
⚠ Common exam trap
A common mix-up: candidates assume adding a cache (DAX) or an index always improves performance and reduces cost, but in reality, these add-ons increase complexity and cost without addressing the core storage cost issue for infrequently accessed data.
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
✓
Use DynamoDB Standard-IA table class for the user profiles table.
DynamoDB Standard-IA (Infrequent Access) table class offers a lower storage cost for data that is accessed infrequently, while still providing the same single-digit millisecond latency for GetItem operations. Since the access pattern is mostly GetItem by user_id, and assuming the data is not accessed frequently enough to justify the higher per-request cost of Standard, Standard-IA can significantly reduce overall costs. The trade-off is a slightly higher per-request cost, but for predominantly read-heavy workloads with low access frequency, the storage savings outweigh the request cost increase.
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 DynamoDB Standard-IA table class for the user profiles table.
Why this is correct
Standard-IA lowers storage cost for infrequently accessed data.
- ✗
Increase the read capacity units to reduce throttling.
Why it's wrong here
Increasing capacity increases cost.
- ✗
Add a Global Secondary Index on an additional attribute.
Why it's wrong here
Adding GSI increases storage and throughput costs.
- ✗
Add DynamoDB Accelerator (DAX) for caching.
Why it's wrong here
DAX adds cost and is for performance, not cost reduction.
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