MLS-C01 Data Engineering Practice Question
A company uses Amazon Kinesis Data Firehose to deliver streaming data to an S3 bucket. The data is JSON and must be partitioned by year, month, and day. The delivery stream is configured with a buffer interval of 60 seconds and buffer size of 5 MB. The data producer sends about 1 MB per second. The data is arriving in S3 but the partitions are not being created as expected. What is the MOST likely reason?
⚠ Common exam trap
It's easy for candidates to assume simply setting a prefix with date-like placeholders (e.g., 'data/year=2025/') is enough, but Firehose requires explicit dynamic partitioning to be enabled and the prefix must use the correct !{timestamp:...} syntax for automatic date-based partitioning.
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 delivery stream does not have dynamic partitioning enabled with the appropriate custom prefix.
Kinesis Data Firehose requires dynamic partitioning to be explicitly enabled and configured with a custom prefix (e.g., 'year=!{timestamp:yyyy}/month=!{timestamp:MM}/day=!{timestamp:dd}/') to automatically partition data by year, month, and day. Without this setting, Firehose writes all data to a single S3 prefix, ignoring the desired partition structure.
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 data is encrypted with AWS KMS and Firehose cannot write to encrypted buckets.
Why it's wrong here
Firehose supports KMS encryption for S3 destinations.
- ✓
The delivery stream does not have dynamic partitioning enabled with the appropriate custom prefix.
Why this is correct
Without dynamic partitioning and the correct prefix, Firehose will not partition the data by year/month/day.
- ✗
The buffer interval is too short for the data volume, causing incomplete records.
Why it's wrong here
Buffer interval does not affect partitioning; it only controls when data is delivered.
- ✗
The S3 bucket has versioning enabled, which prevents partitioning.
Why it's wrong here
Versioning does not prevent partitioning.
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 MLS-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 MLS-C01 exam.