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Question 1,548 of 1,786

Data Store Management →hardMultiple ChoiceObjective-mapped

Query Top N Scores in DynamoDB with Global Secondary Index

This DEA-C01 practice question tests your understanding of data store management. 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 for a gaming leaderboard. The table has a partition key of 'GameId' and a sort key of 'Score'. The application needs to query the top 10 scores for a given game. Which DynamoDB feature should be used for optimal performance?

A
Use a Query operation on the base table with ScanIndexForward set to false.
A Query on the base table with ScanIndexForward false directly retrieves items in descending order by Score because the base table already has Score as sort key. This is the most efficient and cost-effective method.
B
Enable DynamoDB Streams and use a Lambda function to compute the leaderboard.
Why wrong: Streams are for capturing changes, not for real-time queries.
C
Use DynamoDB Accelerator (DAX) to cache the results of a Scan operation.
Why wrong: DAX caches data, but scanning is inefficient for top-N queries.
D
Create a Global Secondary Index with the same partition key and sort key, then query with ScanIndexForward false.
Why wrong: Creating a Global Secondary Index is unnecessary because the base table already has the required partition and sort keys. The GSI would add cost and complexity without performance benefit.

Full breakdown with real-world context →

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 a Query operation on the base table with ScanIndexForward set to false.

Option A is correct because the base table already has 'GameId' as partition key and 'Score' as sort key. A Query operation on the base table with ScanIndexForward set to false retrieves items in descending order by Score, so the first 10 items are the top scores. This is efficient without additional cost or complexity. Option D is unnecessary and incurs extra storage cost.

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 a Query operation on the base table with ScanIndexForward set to false.
Why this is correct
A Query on the base table with ScanIndexForward false directly retrieves items in descending order by Score because the base table already has Score as sort key. This is the most efficient and cost-effective method.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable DynamoDB Streams and use a Lambda function to compute the leaderboard.
Why it's wrong here
Streams are for capturing changes, not for real-time queries.
✗
Use DynamoDB Accelerator (DAX) to cache the results of a Scan operation.
Why it's wrong here
DAX caches data, but scanning is inefficient for top-N queries.
✗
Create a Global Secondary Index with the same partition key and sort key, then query with ScanIndexForward false.
Why it's wrong here
Creating a Global Secondary Index is unnecessary because the base table already has the required partition and sort keys. The GSI would add cost and complexity without performance benefit.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Candidates often mistakenly think they need a GSI when the base table already has the optimal sort key. The trap is to assume that queries on the base table are inefficient, but DynamoDB can efficiently query with the sort key condition and ScanIndexForward.

Detailed technical explanation

How to think about this question

Under the hood, a GSI with a sort key of 'Score' stores items in sorted order by score within each partition key value, enabling DynamoDB to perform a targeted query that reads only the top 10 items using the index's sorted structure. This avoids a full table scan and minimizes read capacity consumption, which is critical for high-traffic leaderboards. In real-world scenarios, you might also consider using a sparse GSI (e.g., only including top scores) to further reduce storage and read costs, but the core mechanism relies on DynamoDB's ability to efficiently traverse the index's B-tree structure in reverse order.

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.

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FAQ

Questions learners often ask

What does this DEA-C01 question test?

Data Store Management — This question tests Data Store Management — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Use a Query operation on the base table with ScanIndexForward set to false. — Option A is correct because the base table already has 'GameId' as partition key and 'Score' as sort key. A Query operation on the base table with ScanIndexForward set to false retrieves items in descending order by Score, so the first 10 items are the top scores. This is efficient without additional cost or complexity. Option D is unnecessary and incurs extra storage cost.

What should I do if I get this DEA-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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Same concept, more angles

1 more ways this is tested on DEA-C01

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. A company uses Amazon DynamoDB for a gaming leaderboard. The table has a primary key of GameId (partition key) and Score (sort key). The application needs to retrieve the top 10 scores for a given game. Which strategies can improve query performance? (Choose TWO.)

medium

A.Change the primary key to a single attribute
✓ B.Create a global secondary index with Score as sort key
C.Use a Scan operation with a limit
D.Increase the write capacity units
✓ E.Use DynamoDB Accelerator (DAX) for caching

Why B: Option B is correct because creating a global secondary index (GSI) with Score as the sort key allows efficient range queries on scores for a given GameId. DynamoDB can then use the GSI to retrieve the top 10 scores in sorted order without scanning the entire table, leveraging the index's sort key to fetch only the highest values.

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