DEA-C01 Data Operations and Support Practice Question
A data pipeline uses Amazon Kinesis Data Firehose to deliver data to an Amazon S3 bucket. The delivery stream is configured with a buffer size of 5 MB and a buffer interval of 60 seconds. The team notices that the S3 objects are much smaller than 5 MB. What is the most likely explanation?
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
✓
The incoming data volume is low, so the 60-second buffer interval triggers delivery before the 5 MB buffer is filled.
If the incoming data rate is low, the buffer interval (60 seconds) expires before the buffer size (5 MB) is reached, causing small objects. Option B is incorrect because S3 event notifications do not split objects; they are triggered by events but do not affect object size. Option C is incorrect because S3 lifecycle policies transition objects to Glacier, which does not affect object size during delivery. Option D is incorrect because GZIP compression reduces the object size after batching, but the buffer interval can still trigger delivery before the buffer is full, so it is not the most likely explanation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The incoming data volume is low, so the 60-second buffer interval triggers delivery before the 5 MB buffer is filled.
Why this is correct
Firehose delivers when either threshold is reached. With low incoming volume, the 5 MB buffer never fills, so the 60-second interval triggers delivery first, producing objects smaller than 5 MB. This directly explains the stem's observation.
- ✗
The S3 bucket has event notifications that split the objects.
Why it's wrong here
S3 event notifications are emitted after objects are written; they cannot split or rewrite an object's contents. It is tempting because notifications commonly trigger downstream processing, and would be correct where a Lambda function must react to each newly delivered Firehose object.
- ✗
The S3 bucket has a lifecycle policy that transitions objects to Glacier.
Why it's wrong here
Lifecycle policies move or expire existing objects; they never alter object size at delivery time. It is tempting because lifecycle rules are a standard S3 cost-control feature, and would be correct where older Firehose-delivered objects must transition to Glacier after a retention period.
- ✗
The delivery stream is using GZIP compression, which reduces the object size.
Why it's wrong here
GZIP compression reduces the size of data in transit and at rest, but it does not cause the S3 objects themselves to be smaller than the buffer size; the buffer size refers to the uncompressed data volume.
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 |
Go deeper
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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.