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 data engineer runs the describe-table command shown in the exhibit. The application frequently queries by CustomerID alone. Currently, these queries result in full table scans. Which action should the engineer take to improve query performance?
Change the sort key to OrderID
Why wrong: The sort key alone does not help query on CustomerID.
Create a local secondary index on CustomerID
Why wrong: LSI requires the same partition key; not helpful.
Increase the read capacity units to 500
Why wrong: More RCUs do not solve the scan issue.
Create a global secondary index on CustomerID
A GSI allows efficient queries on CustomerID.
Answer choices
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 on CustomerID
The `describe-table` output shows CustomerID is the partition key, but the application frequently queries by CustomerID alone, which currently causes full table scans because there is no index supporting that query pattern. Creating a global secondary index (GSI) on CustomerID allows efficient querying by CustomerID without scanning the entire table, as the GSI provides a separate data structure with its own read/write capacity that can be queried directly.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Change the sort key to OrderID
Why it's wrong here
The sort key alone does not help query on CustomerID.
Create a local secondary index on CustomerID
Why it's wrong here
LSI requires the same partition key; not helpful.
Increase the read capacity units to 500
Why it's wrong here
More RCUs do not solve the scan issue.
Create a global secondary index on CustomerID
Why this is correct
A GSI allows efficient queries on CustomerID.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
AWS often tests the misconception that increasing capacity (RCUs/WCUs) can fix query performance issues, but the trap here is that throughput and indexing are separate concerns — full table scans are a design problem, not a capacity problem.
Detailed technical explanation
Under the hood, a GSI on CustomerID creates a separate index table with CustomerID as the partition key, allowing DynamoDB to route queries directly to the relevant items without scanning the base table. This is especially important for access patterns that don't match the base table's key schema, as DynamoDB's query operation can only use the primary key or an index; without an index, a Scan operation is required, which reads every item and is costly in terms of both RCUs and latency. In real-world scenarios, this optimization is critical for high-traffic applications where even a single full table scan can throttle the table and degrade performance for all users.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
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FAQ
Data Store Management — This question tests Data Store Management — Read the scenario before looking for a memorised answer..
The correct answer is: Create a global secondary index on CustomerID — The `describe-table` output shows CustomerID is the partition key, but the application frequently queries by CustomerID alone, which currently causes full table scans because there is no index supporting that query pattern. Creating a global secondary index (GSI) on CustomerID allows efficient querying by CustomerID without scanning the entire table, as the GSI provides a separate data structure with its own read/write capacity that can be queried directly.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This DEA-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DEA-C01 exam.
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