This MLS-C01 practice question tests your understanding of data engineering. 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 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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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.
Option B is correct because 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.
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.
✗
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.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates 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.
Detailed technical explanation
How to think about this question
Dynamic partitioning in Firehose uses inline parsing with expressions like !{partitionKeyFromQuery:key} or !{timestamp:yyyy} to extract partition values from the data or current time. Under the hood, Firehose evaluates these expressions for each buffered batch and writes objects to the corresponding S3 prefix. A common misconfiguration is forgetting to enable 'Dynamic partitioning' in the delivery stream settings and only setting a static prefix.
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Data Engineering — This question tests Data Engineering — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The delivery stream does not have dynamic partitioning enabled with the appropriate custom prefix. — Option B is correct because 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.
What should I do if I get this MLS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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