The correct answer is to create a Global Secondary Index (GSI) with 'CustomerID' as the partition key and 'OrderDate' as the sort key. This is the most efficient approach because a GSI allows you to define an alternative key schema on an existing DynamoDB table, enabling query patterns that the base table’s primary key cannot support directly. Since the base table uses 'OrderID' as the partition key, you cannot efficiently query by 'CustomerID' alone, let alone filter by a date range; the GSI solves this by providing a separate index optimized for that access pattern without modifying the underlying table structure. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of when to use a GSI versus a Local Secondary Index (LSI) — a common trap is choosing an LSI, which requires the same partition key as the base table and cannot be added after table creation. Remember: GSIs are flexible for new query patterns, while LSIs are locked to the base key. Memory tip: “GSI = Go Separate Index” for different partition keys.
DEA-C01 Data Store Management Practice Question
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.
Network Topology
A data engineer ran the above CLI command to describe an Amazon DynamoDB table named 'Orders'. The table has a key schema with 'OrderID' as the partition key and 'CustomerID' as the sort key. The table currently has no items. The engineer wants to add a new attribute 'OrderDate' and then query all orders for a specific customer within a date range. Which of the following actions is the MOST efficient approach to support this query pattern?
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 'CustomerID' as partition key and 'OrderDate' as sort key.
Option D is correct because a Global Secondary Index (GSI) allows querying on a different partition key ('CustomerID') and sort key ('OrderDate') without altering the base table's key schema. This supports efficient range queries on 'OrderDate' for a specific customer, as GSIs provide a separate index with its own provisioned throughput and can be created on existing tables with items. The base table's primary key remains unchanged, and the GSI enables the desired query pattern with low latency.
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.
✗
Modify the table's primary key to include 'OrderDate' as an additional sort key.
Why it's wrong here
Primary key cannot be altered after table creation.
✗
Use a Scan operation with a filter expression on 'CustomerID' and 'OrderDate' to retrieve the data.
Why it's wrong here
Scan is expensive and slow for large tables; it reads every item.
✗
Create a Local Secondary Index (LSI) with 'CustomerID' as partition key and 'OrderDate' as sort key.
Why it's wrong here
LSI must be defined at table creation; it cannot be added later.
✓
Create a Global Secondary Index (GSI) with 'CustomerID' as partition key and 'OrderDate' as sort key.
Why this is correct
GSI can be added at any time and supports efficient queries on CustomerID and OrderDate.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the distinction between LSIs and GSIs, specifically that LSIs require the same partition key as the base table, while GSIs allow a different partition key, which is a common point of confusion for candidates.
Detailed technical explanation
How to think about this question
Under the hood, a GSI is a separate index table that replicates data from the base table, allowing queries on a different partition key and sort key combination. When you create a GSI, DynamoDB automatically copies the base table's attributes (including projected attributes) to the index, and writes to the base table are asynchronously replicated to the GSI, which can introduce eventual consistency. In real-world scenarios, GSIs are ideal for supporting multiple access patterns, such as querying orders by customer and date range, without redesigning the base table schema.
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 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
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 (GSI) with 'CustomerID' as partition key and 'OrderDate' as sort key. — Option D is correct because a Global Secondary Index (GSI) allows querying on a different partition key ('CustomerID') and sort key ('OrderDate') without altering the base table's key schema. This supports efficient range queries on 'OrderDate' for a specific customer, as GSIs provide a separate index with its own provisioned throughput and can be created on existing tables with items. The base table's primary key remains unchanged, and the GSI enables the desired query pattern with low latency.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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 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?
medium
A.Query the table using CustomerID as the partition key
B.Scan the table and filter by CustomerID
C.Use GetItem with CustomerID as the key
✓ D.Create a Global Secondary Index on CustomerID and query the index
Why D: 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.
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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.
Question Discussion
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