The answer is Amazon Timestream, the most cost-effective choice for cost-effective time-series storage for IoT data because it automatically separates recent, frequently queried data into an in-memory store and older, less-accessed data into a magnetic store, directly matching the query pattern of focusing on the last 7 days while retaining a full year of history at minimal cost. This serverless, pay-per-query model eliminates the need to provision or manage storage tiers manually, making it purpose-built for IoT workloads where data volume and query patterns are predictable. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of purpose-built databases versus general-purpose ones like Amazon RDS or DynamoDB, which lack automatic tiering and would incur higher costs for long-term retention of time-series data. A common trap is choosing Amazon S3 with Athena, which works but lacks the optimized time-series functions and automatic tiering that Timestream provides. Remember the memory tip: “Timestream tiers time—hot for the week, cold for the year.”
DEA-C01 Data Store Management Practice Question
This DEA-C01 practice question tests your understanding of data store management. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 needs to store and analyze time-series data from IoT devices. The data volume is 10 GB per day, and the queries are mostly on the most recent 7 days of data. The engineer wants to minimize storage costs while retaining historical data for 1 year. Which combination of AWS services is most cost-effective?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Amazon Timestream
Amazon Timestream is purpose-built for time-series data, offering automatic tiering between in-memory (for recent 7 days) and magnetic stores (for historical data up to 1 year). This matches the query pattern (mostly recent 7 days) and retention requirement (1 year) while minimizing storage costs through its serverless, pay-per-query model. Timestream also supports time-series-specific functions like interpolation and smoothing, making it more efficient than general-purpose databases for this workload.
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.
✓
Amazon Timestream
Why this is correct
Timestream is cost-effective for time-series data with automatic storage tiering.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Amazon DynamoDB with TTL and S3 for archival
Why it's wrong here
This can work but is less cost-effective and more complex than Timestream.
✗
Amazon Redshift
Why it's wrong here
Redshift is more expensive and designed for analytic queries, not time-series specifically.
✗
Amazon RDS with MySQL
Why it's wrong here
RDS is not optimized for time-series data and can be costly for high-volume writes.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose DynamoDB with TTL and S3 for archival (Option B) because it seems cost-effective, but they overlook the operational complexity and query latency of accessing historical data in S3, which violates the 'minimize storage costs while retaining historical data for 1 year' requirement without considering query patterns.
Detailed technical explanation
How to think about this question
Timestream uses a dual-storage architecture: a memory store (SSD-backed) for recent data with millisecond query latency, and a magnetic store (cost-optimized) for historical data with second-level latency. Data is automatically moved from memory to magnetic based on a configurable retention policy (e.g., 7 days in memory, 365 days total). Under the hood, Timestream compresses and partitions data by time, enabling efficient range scans and aggregate queries without manual indexing or sharding.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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: Amazon Timestream — Amazon Timestream is purpose-built for time-series data, offering automatic tiering between in-memory (for recent 7 days) and magnetic stores (for historical data up to 1 year). This matches the query pattern (mostly recent 7 days) and retention requirement (1 year) while minimizing storage costs through its serverless, pay-per-query model. Timestream also supports time-series-specific functions like interpolation and smoothing, making it more efficient than general-purpose databases for this workload.
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: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
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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