- A
Amazon Athena
Why wrong: Athena is an interactive query service, not for real-time transformation.
- B
Amazon Kinesis Data Analytics
Why wrong: Data Analytics is for running SQL on streams, not for record transformation.
- C
Amazon EMR
Why wrong: EMR is not designed for inline transformations within Firehose.
- D
AWS Lambda
Lambda can be invoked by Firehose to transform records in real time.
Question 1,534 of 1,755
Redact PII in Real Time with Kinesis Firehose and AWS Lambda
This MLS-C01 practice question tests your understanding of data engineering. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 Amazon S3. The data contains personally identifiable information (PII) that must be redacted before storage. Which AWS service can be integrated with Kinesis Data Firehose to transform the data in real time?
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
✓
AWS Lambda
AWS Lambda can be integrated as a data transformation function within a Kinesis Data Firehose delivery stream. When Firehose receives incoming records, it can invoke a Lambda function synchronously to process each batch of data, allowing you to redact PII fields in real time before the data is written to Amazon S3.
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.
- ✗
Amazon Athena
Why it's wrong here
Athena is an interactive query service, not for real-time transformation.
- ✗
Amazon Kinesis Data Analytics
Why it's wrong here
Data Analytics is for running SQL on streams, not for record transformation.
- ✗
Amazon EMR
Why it's wrong here
EMR is not designed for inline transformations within Firehose.
- ✓
AWS Lambda
Why this is correct
Lambda can be invoked by Firehose to transform records in real time.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Kinesis Data Analytics for transformation, but it is designed for real-time analytics and pattern detection, not for inline record-by-record data masking or redaction within a Firehose delivery stream.
Detailed technical explanation
How to think about this question
Under the hood, Kinesis Data Firehose invokes the configured Lambda function synchronously with a batch of records (up to 3 MB or 6 MB depending on the source), and the function must return the transformed records within a 60-second timeout. The Lambda function receives records in base64-encoded format and must return them in the same structure, allowing you to parse, redact, and re-encode each record. A real-world scenario might involve redacting credit card numbers or email addresses from clickstream data before landing in a data lake for compliance with GDPR or PCI DSS.
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.
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 |
What to study next
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FAQ
Questions learners often ask
What does this MLS-C01 question test?
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: AWS Lambda — AWS Lambda can be integrated as a data transformation function within a Kinesis Data Firehose delivery stream. When Firehose receives incoming records, it can invoke a Lambda function synchronously to process each batch of data, allowing you to redact PII fields in real time before the data is written to Amazon S3.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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.
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