DBS-C01 Workload-Specific Database Design Practice Question
This DBS-C01 practice question tests your understanding of workload-specific database design. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A media company stores video metadata in Amazon DynamoDB. Each record has a partition key of video_id and a sort key of uploaded_timestamp. The application frequently queries videos by genre and upload date. The access pattern is read-heavy with occasional writes. The table is provisioned with 3000 RCUs and 1000 WCUs. The company notices that queries by genre are slow and consume many RCUs. Which design change should be made to optimize for this workload?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a global secondary index (GSI) with genre as partition key and uploaded_timestamp as sort key.
Option D is correct because creating a Global Secondary Index (GSI) with genre as the partition key and uploaded_timestamp as the sort key allows efficient querying by genre and date without scanning the entire table. This directly supports the access pattern, reducing RCU consumption by using index key lookups instead of full table scans. The GSI is ideal for read-heavy workloads with occasional writes, as it offloads query traffic from the main table.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 Accelerator (DAX) to cache query results.
Why it's wrong here
DAX caches results but does not improve the efficiency of the query pattern itself.
✗
Create a local secondary index (LSI) with genre as sort key and uploaded_timestamp as partition key.
Why it's wrong here
LSI must have the same partition key as the base table; genre cannot be the partition key.
✗
Increase the provisioned RCUs to 6000.
Why it's wrong here
Increasing RCUs does not reduce the cost of inefficient queries; it only provides more capacity.
✓
Create a global secondary index (GSI) with genre as partition key and uploaded_timestamp as sort key.
Why this is correct
A GSI with genre as partition key allows efficient queries by genre and date.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse LSIs and GSIs, incorrectly assuming an LSI can change the partition key, when in fact LSIs must share the main table's partition key, making them unsuitable for querying by a different attribute like genre.
Detailed technical explanation
How to think about this question
A Global Secondary Index (GSI) in DynamoDB maintains a separate partition key (genre) and sort key (uploaded_timestamp), enabling efficient range queries on upload date within a genre. Under the hood, the GSI is a separate table with its own provisioned throughput, so writes to the main table incur additional WCU consumption for index updates—a trade-off that must be accounted for in capacity planning. In a read-heavy workload with occasional writes, this trade-off is acceptable, but in write-heavy scenarios, the extra WCU cost could become significant.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a global secondary index (GSI) with genre as partition key and uploaded_timestamp as sort key. — Option D is correct because creating a Global Secondary Index (GSI) with genre as the partition key and uploaded_timestamp as the sort key allows efficient querying by genre and date without scanning the entire table. This directly supports the access pattern, reducing RCU consumption by using index key lookups instead of full table scans. The GSI is ideal for read-heavy workloads with occasional writes, as it offloads query traffic from the main table.
What should I do if I get this DBS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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