The correct solution is to create a global secondary index with device_id as the partition key and a truncated timestamp as the sort key to distribute writes. This improves DynamoDB time-series query performance by breaking up the write traffic that would otherwise concentrate on a single partition for high-volume devices. When a device generates large amounts of data, all writes target the same partition key, creating a hot partition that throttles reads and increases latency. By truncating the timestamp—for example, to the hour or day—and using it as the GSI sort key, the index spreads writes across multiple physical partitions while still allowing efficient range queries for a specific device over a time window. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of partition design for time-series workloads; a common trap is to assume that adding more read capacity units alone will fix the issue, but the root cause is write distribution. Remember the memory tip: “Truncate the time to spread the load—hot partitions slow the road.”
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.
A data engineering team is using Amazon DynamoDB to store time-series data for a monitoring application. The table has a primary key of device_id (partition key) and timestamp (sort key). The application queries data for a specific device over a time range. The team notices that read latency is high for devices that generate large amounts of data. They need to improve query performance. Which solution should they implement?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
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 with device_id as partition key and a truncated timestamp as sort key to distribute writes.
Option C is correct because creating a global secondary index (GSI) with device_id as the partition key and a truncated timestamp as the sort key helps distribute write traffic more evenly across partitions. This reduces hot partitions caused by devices that generate large amounts of data, thereby improving read latency by preventing throttling and reducing contention on a single partition.
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.
✗
Enable DynamoDB Accelerator (DAX) for the table.
Why it's wrong here
Caches reads but does not address hot partition writes.
✗
Change the application to use eventually consistent reads.
Why it's wrong here
May not be acceptable for the monitoring application.
✓
Create a global secondary index with device_id as partition key and a truncated timestamp as sort key to distribute writes.
Why this is correct
Helps spread write load and improve read performance for time-range queries.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the read capacity units for the table.
Why it's wrong here
Does not address hot partition due to write patterns.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often mistake high read latency as a pure read-throughput issue and choose to increase RCUs or add DAX, overlooking the fact that the real bottleneck is write-side hot partitions causing throttling and increased latency for reads on that partition.
Detailed technical explanation
How to think about this question
Under the hood, DynamoDB partitions data based on the partition key's hash value. When a single device_id generates a high volume of writes, all those writes land on the same partition, creating a hot spot. A GSI with a truncated timestamp (e.g., rounding to the hour) as the sort key spreads writes across multiple partitions because the truncated timestamp changes over time, effectively distributing the load. This technique is known as write sharding and is a common pattern for time-series data to avoid throttling and improve query performance.
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 with device_id as partition key and a truncated timestamp as sort key to distribute writes. — Option C is correct because creating a global secondary index (GSI) with device_id as the partition key and a truncated timestamp as the sort key helps distribute write traffic more evenly across partitions. This reduces hot partitions caused by devices that generate large amounts of data, thereby improving read latency by preventing throttling and reducing contention on a single partition.
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.
Are there clue words in this question I should notice?
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
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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