The correct answer is to create a Global Secondary Index (GSI) on the region attribute. This design approach directly addresses the need for DynamoDB GSI for region-based queries to avoid scans, because a GSI provides an alternative query path that allows you to efficiently retrieve all active users in a specific region using a targeted index scan rather than a costly full table scan. By partitioning the data by region in the GSI, you drastically reduce read capacity consumption and eliminate throttling, while the base table remains optimized for single-digit millisecond user ID lookups. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of when to use GSIs versus Local Secondary Indexes (LSIs) or scan operations—a common trap is reaching for filters or pagination on the base table, which still incurs full scan costs. Remember the memory tip: “GSI for geography, base table for ID—scan only when you have to, index when you query by.”
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 company uses Amazon DynamoDB as the primary database for a global gaming application. The application requires single-digit millisecond latency for user profile lookups by user ID. However, some queries need to retrieve all active users in a region (e.g., 'us-east-1') for administrative dashboards, and these queries currently perform full table scans, causing high costs and throttling. What design approach should be taken to optimize this?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
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) on the region attribute.
Option C is correct because creating a Global Secondary Index (GSI) on the 'region' attribute allows the administrative dashboard queries to retrieve all active users in a specific region using an efficient index scan instead of a full table scan. This reduces read capacity consumption, avoids throttling, and maintains single-digit millisecond latency for the indexed queries, while the base table remains optimized for user ID lookups.
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.
✗
Implement DynamoDB Accelerator (DAX) to cache the dashboard queries.
Why it's wrong here
DAX caches individual item queries, not scan/query results for arbitrary attributes.
✗
Increase the read capacity units (RCUs) on the base table.
Why it's wrong here
Increasing capacity does not eliminate the scan; it only reduces throttling but increases cost.
✓
Create a global secondary index (GSI) on the region attribute.
Why this is correct
A GSI allows efficient querying on region without scanning the base table, reducing cost and throttling.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create a local secondary index (LSI) on the region attribute.
Why it's wrong here
LSI requires the same partition key as the base table and cannot be used to query by region alone.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse LSIs with GSIs, assuming an LSI can be used to query by a non-key attribute like region, but LSIs are limited to the same partition key as the base table and cannot avoid a full scan when the query predicate is on a different partition key.
Detailed technical explanation
How to think about this question
A Global Secondary Index (GSI) in DynamoDB has its own partition and sort keys, allowing efficient querying on non-key attributes like 'region' without affecting the base table's schema. Under the hood, the GSI is a separate table that is asynchronously updated, so eventual consistency applies; for administrative dashboards, this is acceptable. In a real-world scenario, if the 'region' attribute has low cardinality (e.g., only a few regions), consider using a composite sort key (e.g., 'region#status') or a sparse index to further optimize queries for active users only.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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) on the region attribute. — Option C is correct because creating a Global Secondary Index (GSI) on the 'region' attribute allows the administrative dashboard queries to retrieve all active users in a specific region using an efficient index scan instead of a full table scan. This reduces read capacity consumption, avoids throttling, and maintains single-digit millisecond latency for the indexed queries, while the base table remains optimized for user ID lookups.
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.
Are there clue words in this question I should notice?
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
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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