The answer is to increase the Kinesis Data Firehose buffer size to 100 MB and the buffer interval to 300 seconds. This works because Firehose writes to S3 only when either the buffer size or the buffer interval is reached first; by raising both thresholds, you allow more small JSON events to accumulate before the delivery trigger fires, directly addressing the low-volume scenario where the default 10 MB and 60 seconds produce tiny 5 MB files. On the AWS Certified Data Engineer Associate DEA-C01 exam, this tests your understanding of Firehose’s buffering mechanics as a cost-optimization tool—a common trap is to over-engineer with Lambda or Glue when simply tuning the native buffer settings suffices. Remember the mnemonic “Bigger Buffer, Longer Wait” to recall that both size and interval must be increased together to aggregate into larger files.
DEA-C01 Data Ingestion and Transformation Practice Question
This DEA-C01 practice question tests your understanding of data ingestion and transformation. 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 gaming company ingests player event data from mobile games into Amazon Kinesis Data Streams. Each event is a small JSON payload (<1 KB). The data must be delivered to Amazon S3 for analytics, and the company wants to minimize storage costs by aggregating events into larger files (e.g., 100 MB per file). The current setup uses Kinesis Data Firehose with a buffer size of 10 MB and a buffer interval of 60 seconds, but the resulting files are very small (average 5 MB) because the data volume is low. The engineer needs to ensure that files are at least 100 MB to reduce the number of S3 objects and lower costs. What should the engineer do?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "least"
Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
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
✓
Increase the buffer size in Kinesis Data Firehose to 100 MB and increase the buffer interval to 300 seconds.
Option D is correct: Increase the buffer size to 100 MB and the buffer interval to 300 seconds to allow more data to accumulate before writing. Option A (Lambda) would not aggregate efficiently. Option B (Glue) adds latency and cost. Option C (EMR) is overkill.
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.
✗
Use an AWS Glue streaming ETL job with a 100 MB file size threshold to write to S3.
Why it's wrong here
Glue streaming adds complexity and cost; Firehose is simpler for this use case.
✗
Use an AWS Lambda function to buffer events in memory and write to S3 when buffer reaches 100 MB.
Why it's wrong here
Lambda has memory and timeout limits; it is not designed for long-lived buffering.
✓
Increase the buffer size in Kinesis Data Firehose to 100 MB and increase the buffer interval to 300 seconds.
Why this is correct
This allows Firehose to accumulate data until the buffer size or interval is reached, producing larger files.
Clue confirmation
The clue words "least", "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use Amazon EMR with Spark Streaming to aggregate and write larger files to S3.
Why it's wrong here
EMR requires cluster management and is overkill.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 DEA-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Data Ingestion and Transformation — This question tests Data Ingestion and Transformation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Increase the buffer size in Kinesis Data Firehose to 100 MB and increase the buffer interval to 300 seconds. — Option D is correct: Increase the buffer size to 100 MB and the buffer interval to 300 seconds to allow more data to accumulate before writing. Option A (Lambda) would not aggregate efficiently. Option B (Glue) adds latency and cost. Option C (EMR) is overkill.
What should I do if I get this DEA-C01 question wrong?
Identify which DEA-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "least", "minimum / minimize". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
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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