DEA-C01 Data Ingestion and Transformation Practice Question
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?
⚠ Common exam trap
Watch out — candidates often 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.
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.
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
Firehose flushes when either the 5 MB buffer fills or 60 seconds elapses. At 2 MB/s the size threshold is reached first, after roughly 2.5 seconds, so writes occur far more frequently than the configured interval.
- ✗
Approximately 30 seconds
Why it's wrong here
Thirty seconds would require roughly 167 KB per second to fill 5 MB, but 2 MB per second reaches the size threshold in about 2.5 seconds. The 30-second figure misreads the interval as half the configured 60 seconds.
- ✗
Approximately 60 seconds
Why it's wrong here
The 60-second buffer interval is an upper bound, not the trigger here: at 2 MB per second the 5 MB buffer fills in about 2.5 seconds, so Firehose flushes on size first. The interval governs only low-throughput streams.
- ✗
Approximately 10 seconds
Why it's wrong here
Ten seconds corresponds to neither threshold: 5 MB at 2 MB per second fills in about 2.5 seconds, and the interval is 60 seconds. The figure appears to divide the buffer size by an unrelated rate.
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 |
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.