DEA-C01 Data Store Management Practice Question
A data engineer is building an Amazon DynamoDB table that will store IoT sensor readings. Each reading has a deviceId (partition key) and a timestamp (sort key). The team wants to retrieve all readings for a device within the last 24 hours, and they also want to minimize the number of read capacity units consumed. Which access pattern should the engineer implement?
⚠ Common exam trap
The trap here is reaching for a secondary index or a Scan when the base table's composite key already supports the access pattern, wasting capacity and money.
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
✓
Issue a Query operation with the partition key equal to the deviceId and a key condition expression on the sort key using a BETWEEN clause for the timestamp range.
The table already has deviceId as the partition key and timestamp as the sort key, which is the ideal design for retrieving a device's readings over a time range. Querying that partition with a BETWEEN condition on the sort key reads only the matching items, minimizing consumed read capacity. Scan, parallel Scan, and a GSI on timestamp all read or return excessive data.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create a global secondary index on timestamp and Query it with a key condition on the timestamp range.
Why it's wrong here
A GSI on timestamp alone does not let you constrain reads to one device, so a Query against it would scan across all devices in the time window. That returns and consumes capacity for many unrelated items, and maintaining the index adds write cost. It does not satisfy the per-device retrieval requirement efficiently.
- ✓
Issue a Query operation with the partition key equal to the deviceId and a key condition expression on the sort key using a BETWEEN clause for the timestamp range.
Why this is correct
Query targets a single partition, and adding a key condition on the sort key restricts the read to the requested timestamp range. DynamoDB reads only the items within that range, so consumed read capacity is proportional to the matching items, which is the most efficient way to satisfy the access pattern described.
- ✗
Use a parallel Scan with multiple segments and a FilterExpression on deviceId.
Why it's wrong here
Parallel Scan speeds up a full-table Scan by dividing it into segments, but it still reads the entire table and applies filters after reading. It consumes more total read capacity than a targeted Query and ignores the composite key. It is inappropriate when a known partition and sort key range can be queried directly.
- ✗
Issue a Scan operation on the table with a FilterExpression on deviceId and timestamp.
Why it's wrong here
Scan reads every item in the table and then applies the filter, so it consumes read capacity proportional to the whole table size, not the returned items. With a growing IoT dataset this is both slow and expensive, and it does not use the composite key ordering. It directly contradicts the goal of minimizing consumed read capacity.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
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.