This DEA-C01 practice question tests your understanding of data store management. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Network Topology
A data engineer runs the above CLI command to describe the DynamoDB table 'Orders'. The table has a partition key 'OrderID' and sort key 'CustomerID'. Which query operation is most efficient for retrieving all orders for a specific customer?
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 and query the index
Option D is correct because a Global Secondary Index (GSI) on CustomerID allows you to query efficiently using CustomerID as the partition key, avoiding a full table scan. Since the base table's primary key is (OrderID, CustomerID), you cannot directly query by CustomerID alone; a GSI provides an alternative access pattern optimized for this query.
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.
✗
Query the table using CustomerID as the partition key
Why it's wrong here
CustomerID is the sort key, not partition key; can only query by partition key.
✗
Scan the table and filter by CustomerID
Why it's wrong here
Scan reads all items, which is costly and slow.
✗
Use GetItem with CustomerID as the key
Why it's wrong here
GetItem requires the full primary key (OrderID and CustomerID).
✓
Create a Global Secondary Index on CustomerID and query the index
Why this is correct
A GSI allows efficient query by CustomerID alone.
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 assume the sort key can be used as a query filter without an index, but DynamoDB requires the partition key for Query operations, and a Scan is often mistakenly chosen as a simpler alternative despite its performance cost.
Detailed technical explanation
How to think about this question
Under the hood, DynamoDB distributes data across partitions based on the partition key hash. A GSI on CustomerID creates a separate index with its own partition key, enabling efficient querying without scanning the base table. In real-world scenarios, this pattern is critical for high-traffic applications where scanning would exceed provisioned throughput and increase latency.
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.
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: Create a Global Secondary Index on CustomerID and query the index — Option D is correct because a Global Secondary Index (GSI) on CustomerID allows you to query efficiently using CustomerID as the partition key, avoiding a full table scan. Since the base table's primary key is (OrderID, CustomerID), you cannot directly query by CustomerID alone; a GSI provides an alternative access pattern optimized for this query.
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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Question Discussion
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