DEA-C01 Data Operations and Support Practice Question
A company uses Amazon Kinesis Data Firehose to deliver streaming data to Amazon S3. The data is in JSON format, and each record is approximately 5 KB. The company has set the buffer interval to 60 seconds and the buffer size to 5 MB. However, the data engineer observes that the delivery to S3 is delayed by up to 5 minutes during peak traffic. The engineer wants to reduce the delivery latency to under 1 minute. Which TWO actions should the engineer take? (Choose TWO.)
⚠ Common exam trap
The trap is assuming compression or format conversion (GZIP, Parquet) reduces delivery latency, when only the buffer size and buffer interval thresholds control when Firehose actually flushes data to S3.
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
✓
Reduce the buffer size to 1 MB.
Option B is correct because Kinesis Data Firehose flushes data to S3 when either the buffer size OR the buffer interval is reached; lowering the buffer size from 5 MB to 1 MB makes the size threshold trigger much sooner, so smaller batches are delivered more frequently and latency drops. Option E is correct because reducing the buffer interval from 60 seconds to 10 seconds forces a flush at least every 10 seconds even if the buffer size is not reached, directly capping delivery latency well under 1 minute. Together, B and E ensure the delivery stream flushes on the shorter of the two thresholds, which is exactly what is needed to cut the observed 5-minute delays. Option A does not help because GZIP compression only reduces payload size and can actually add CPU overhead, not reduce flush latency. Option C is wrong because increasing the buffer size to 50 MB would delay flushes further, worsening latency. Option D is wrong because converting to Parquet changes the storage format and query efficiency, not the Firehose buffering/flush timing that governs delivery latency.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable GZIP compression for the delivery stream.
Why it's wrong here
GZIP compression shrinks delivered object size but does not change when Firehose triggers a flush, so it cannot bring latency below one minute. It is tempting because compression lowers S3 storage and transfer costs, which suits cost-optimisation goals rather than latency reduction.
- ✓
Reduce the buffer size to 1 MB.
Why this is correct
Firehose flushes when either the buffer size or buffer interval is reached, whichever comes first. Lowering the size to 1 MB means the 5 MB threshold is hit sooner, triggering delivery earlier during peak traffic and cutting latency below one minute.
- ✗
Increase the buffer size to 50 MB.
Why it's wrong here
Raising the buffer size to 50 MB makes Firehose wait longer before flushing, increasing rather than reducing delivery latency. It is tempting because larger buffers improve compression and reduce the number of S3 objects, which suits throughput-oriented, latency-tolerant pipelines.
- ✗
Convert the data format to Apache Parquet before delivery.
Why it's wrong here
Parquet conversion changes storage format and query efficiency, not how quickly Firehose flushes buffered records to S3. It is tempting because Parquet reduces downstream scan costs and suits analytics workloads, but latency here is governed by buffer interval and buffer size settings.
- ✓
Reduce the buffer interval to 10 seconds.
Why this is correct
Firehose delivers when the buffer interval elapses or the buffer fills. Reducing the interval to 10 seconds forces more frequent flushes regardless of accumulated volume, directly addressing the peak-traffic delay and bringing delivery latency under one minute.
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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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
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.