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Question 1,039 of 1,740

Monitoring and Logging →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is to use a CloudWatch Logs subscription filter that invokes an AWS Lambda function to mask sensitive data before storage. This solution is correct because the subscription filter acts as a real-time trigger, streaming each log event directly to Lambda as it arrives, allowing the function to apply regex-based masking—such as replacing credit card numbers with asterisks—and then write the sanitized logs to a separate log group without any changes to the application code or additional infrastructure like Kinesis. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of serverless log processing patterns and the principle of least operational overhead; a common trap is overcomplicating the solution with Kinesis Data Firehose or a third-party tool when a simple Lambda filter suffices. Remember the mnemonic: “Filter, Mask, Forward”—the subscription filter triggers the mask, then forwards clean logs to a new group.

DOP-C02 Monitoring and Logging Practice Question

This DOP-C02 practice question tests your understanding of monitoring and logging. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.

An application running on Amazon ECS Fargate writes logs to CloudWatch Logs. The logs include sensitive data such as credit card numbers, which must be masked before storage. What is the most cost-effective solution that requires the least operational overhead?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "least"
Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.

Question 1mediummultiple choice

Full question →

A
Stream logs to Amazon Kinesis Data Firehose with a Lambda transformation, then deliver to CloudWatch Logs.
Why wrong: Adds Kinesis cost and complexity; Lambda transformation is similar but extra hop.
B
Configure a CloudWatch Logs subscription to stream logs to Amazon S3, and use S3 Object Lambda to mask data on retrieval.
Why wrong: Object Lambda masks on retrieval but does not mask at rest; sensitive data remains in S3.
C
Deploy a sidecar container in the ECS task that reads logs from stdout, masks data, and sends to CloudWatch Logs.
Why wrong: Requires custom container and increases operational overhead.
D
Use a CloudWatch Logs subscription filter to invoke an AWS Lambda function that masks sensitive data and writes the sanitized logs to a different log group.
This masks data before storage, is serverless, and cost-effective.

Full breakdown with real-world context →

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

✓

Use a CloudWatch Logs subscription filter to invoke an AWS Lambda function that masks sensitive data and writes the sanitized logs to a different log group.

Option D is correct because CloudWatch Logs subscription filters can invoke a Lambda function in real-time as logs are ingested, allowing the function to mask sensitive data (e.g., credit card numbers) and write the sanitized logs to a different log group. This approach requires no additional infrastructure, no streaming services, and no changes to the application code, making it the most cost-effective and operationally lightweight solution.

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.

✗
Stream logs to Amazon Kinesis Data Firehose with a Lambda transformation, then deliver to CloudWatch Logs.
Why it's wrong here
Adds Kinesis cost and complexity; Lambda transformation is similar but extra hop.
✗
Configure a CloudWatch Logs subscription to stream logs to Amazon S3, and use S3 Object Lambda to mask data on retrieval.
Why it's wrong here
Object Lambda masks on retrieval but does not mask at rest; sensitive data remains in S3.
✗
Deploy a sidecar container in the ECS task that reads logs from stdout, masks data, and sends to CloudWatch Logs.
Why it's wrong here
Requires custom container and increases operational overhead.
✓
Use a CloudWatch Logs subscription filter to invoke an AWS Lambda function that masks sensitive data and writes the sanitized logs to a different log group.
Why this is correct
This masks data before storage, is serverless, and cost-effective.
Clue confirmation
The clue word "least" in the question point toward this answer.
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 choose Option A or C because they assume a streaming pipeline or sidecar is required for log transformation, but they overlook that CloudWatch Logs subscription filters with Lambda provide a native, serverless, and cost-effective alternative that avoids additional services and infrastructure changes.

Trap categories for this question

Similar concept trap
Adds Kinesis cost and complexity; Lambda transformation is similar but extra hop.

Detailed technical explanation

How to think about this question

CloudWatch Logs subscription filters use a real-time, near-synchronous invocation of Lambda via the CloudWatch Logs API, where the log events are base64-encoded and gzip-compressed in the event payload. The Lambda function must decode, decompress, apply regex-based masking (e.g., for PCI DSS compliance), and then use the PutLogEvents API to write to a different log group; this ensures the original log group never contains sensitive data. In a real-world scenario, this pattern is commonly used for GDPR or HIPAA compliance where logs must be sanitized before long-term storage.

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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.

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.

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FAQ

Questions learners often ask

What does this DOP-C02 question test?

Monitoring and Logging — This question tests Monitoring and Logging — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Use a CloudWatch Logs subscription filter to invoke an AWS Lambda function that masks sensitive data and writes the sanitized logs to a different log group. — Option D is correct because CloudWatch Logs subscription filters can invoke a Lambda function in real-time as logs are ingested, allowing the function to mask sensitive data (e.g., credit card numbers) and write the sanitized logs to a different log group. This approach requires no additional infrastructure, no streaming services, and no changes to the application code, making it the most cost-effective and operationally lightweight solution.

What should I do if I get this DOP-C02 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: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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This DOP-C02 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 DOP-C02 exam.