- A
Approximately 2.5 seconds
The buffer size of 5 MB fills in 2.5 seconds at 2 MB/s, triggering a write.
- B
Approximately 30 seconds
Why wrong: This is not consistent with the data rate.
- C
Approximately 60 seconds
Why wrong: The buffer interval is 60 seconds, but the size threshold triggers earlier.
- D
Approximately 10 seconds
Why wrong: This would require a data rate of 0.5 MB/s.
Question 124 of 1,786
Kinesis Data Firehose Buffer Interval vs Size
This DEA-C01 practice question tests your understanding of data ingestion and transformation. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 pipeline uses Amazon Kinesis Data Firehose to deliver data to an S3 bucket. The delivery stream is configured with a buffer interval of 60 seconds and a buffer size of 5 MB. The data arrives at an average rate of 2 MB per second. What is the expected time interval between S3 writes?
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
✓
Approximately 2.5 seconds
Amazon Kinesis Data Firehose writes to S3 when either the buffer interval (60 seconds) or buffer size (5 MB) is reached first. With data arriving at 2 MB/s, the 5 MB buffer fills in 2.5 seconds (5 MB / 2 MB/s), triggering a write before the 60-second interval expires. Thus, the expected time between S3 writes is approximately 2.5 seconds.
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.
- ✓
Approximately 2.5 seconds
Why this is correct
The buffer size of 5 MB fills in 2.5 seconds at 2 MB/s, triggering a write.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Approximately 30 seconds
Why it's wrong here
This is not consistent with the data rate.
- ✗
Approximately 60 seconds
Why it's wrong here
The buffer interval is 60 seconds, but the size threshold triggers earlier.
- ✗
Approximately 10 seconds
Why it's wrong here
This would require a data rate of 0.5 MB/s.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume the buffer interval (60 seconds) is the primary determinant of write frequency, ignoring that the buffer size threshold triggers writes much earlier when data arrival rates are high.
Detailed technical explanation
How to think about this question
Kinesis Data Firehose uses a 'first-trigger-wins' policy between buffer size and buffer interval; the buffer size is checked per shard-level accumulation, and the actual write frequency can vary with data arrival patterns. In real-world scenarios, bursty traffic may cause writes to occur even faster than the average rate suggests, while idle periods extend intervals up to the buffer interval maximum. Understanding this interplay is critical for optimizing S3 write costs and downstream processing 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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
What to study next
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FAQ
Questions learners often ask
What does this DEA-C01 question test?
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: Approximately 2.5 seconds — Amazon Kinesis Data Firehose writes to S3 when either the buffer interval (60 seconds) or buffer size (5 MB) is reached first. With data arriving at 2 MB/s, the 5 MB buffer fills in 2.5 seconds (5 MB / 2 MB/s), triggering a write before the 60-second interval expires. Thus, the expected time between S3 writes is approximately 2.5 seconds.
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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Last reviewed: Jul 4, 2026
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.
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