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 engineer needs to store semi-structured JSON data from IoT devices. The data is written once, read rarely, but must be queryable using SQL. The storage cost must be minimized. Which storage solution should the engineer choose?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Store JSON files in Amazon S3 and use Amazon Athena for queries
Amazon S3 provides the lowest-cost storage for data that is written once and rarely read, while Amazon Athena enables serverless SQL querying directly on JSON files stored in S3. This combination minimizes storage costs because S3 charges only for the data stored and retrieval, with no minimum fees or provisioning required, and Athena charges only for the data scanned per query. The workload's write-once, read-rarely pattern aligns perfectly with S3's durability and lifecycle policies, making it the most cost-effective choice.
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.
✗
Store JSON in Amazon Redshift as SUPER data type
Why it's wrong here
Redshift is for analytics and has higher storage cost than S3.
✗
Store JSON in an Amazon RDS for MySQL table
Why it's wrong here
RDS storage costs more than S3 and requires schema management.
✗
Store JSON documents in Amazon DynamoDB and use PartiQL for queries
Why it's wrong here
DynamoDB is optimized for frequent access; cost per GB is higher than S3.
✓
Store JSON files in Amazon S3 and use Amazon Athena for queries
Why this is correct
S3 provides low-cost storage; Athena enables SQL querying over JSON.
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 often choose DynamoDB (Option C) because it supports JSON natively and PartiQL provides SQL-like queries, but they overlook that DynamoDB's provisioned throughput and storage costs are significantly higher than S3 for write-once, read-rarely workloads, and that Athena on S3 is the serverless, cost-optimized solution for ad-hoc SQL queries on infrequently accessed data.
Detailed technical explanation
How to think about this question
Amazon S3 stores JSON files as objects, and Athena uses the Presto engine with a built-in JSON SerDe (org.apache.hive.hcatalog.data.JsonSerDe) to parse the data at query time, allowing schema-on-read without any ETL. A subtle behavior is that Athena charges based on the amount of data scanned per query, so partitioning the S3 data by date or device ID can drastically reduce costs by limiting the scanned data. In a real-world scenario, a data engineer might use S3 Lifecycle policies to transition older JSON files to S3 Glacier Deep Archive for even lower storage costs, while still being able to query them via Athena if needed, though with higher 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 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: Store JSON files in Amazon S3 and use Amazon Athena for queries — Amazon S3 provides the lowest-cost storage for data that is written once and rarely read, while Amazon Athena enables serverless SQL querying directly on JSON files stored in S3. This combination minimizes storage costs because S3 charges only for the data stored and retrieval, with no minimum fees or provisioning required, and Athena charges only for the data scanned per query. The workload's write-once, read-rarely pattern aligns perfectly with S3's durability and lifecycle policies, making it the most cost-effective choice.
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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