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Data Ingestion and Transformation →mediumMultiple ChoiceObjective-mapped

DEA-C01 Data Ingestion and Transformation Practice Question

This DEA-C01 practice question tests your understanding of data ingestion and transformation. 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 social media company ingests user activity data from multiple sources using Amazon Kinesis Data Firehose. The data is delivered to Amazon S3 in near-real-time. The company wants to transform the data by adding a timestamp and masking email addresses before storing it in S3. The transformation should be applied to all records. What is the most cost-effective way to implement this transformation?

A
Use Amazon Athena to run a CTAS query that transforms the data and writes to a new location.
Why wrong: Athena is for querying, not for real-time transformation in the ingestion pipeline.
B
Use AWS Glue to schedule a batch job every 5 minutes to transform the data.
Why wrong: Batch processing adds latency and is not cost-effective for near-real-time.
C
Use Amazon S3 Events to trigger a Lambda function whenever a new object is created.
Why wrong: This would process files after they are stored, not before, and incurs additional S3 costs.
D
Configure the Firehose delivery stream to invoke a Lambda function for data transformation.
Firehose supports built-in Lambda transformation for real-time processing.

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

✓

Configure the Firehose delivery stream to invoke a Lambda function for data transformation.

The most cost-effective way is to configure the Kinesis Data Firehose delivery stream to invoke an AWS Lambda function for data transformation before the data is delivered to S3. This approach is serverless and only runs when data is flowing, so you pay only for the compute time used during transformation. Option A (Athena CTAS) would require querying after storage, adding cost and latency. Option B (Glue batch job) runs on a schedule regardless of data volume, leading to idle costs, and introduces latency. Option C (S3 Events with Lambda) triggers after data is already stored, meaning the data is first stored in raw form, then transformed, doubling storage costs and adding complexity. Therefore, the Firehose-integrated Lambda is the most cost-effective and low-latency option.

Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
Use Amazon Athena to run a CTAS query that transforms the data and writes to a new location.
Why it's wrong here
Athena is for querying, not for real-time transformation in the ingestion pipeline.
✗
Use AWS Glue to schedule a batch job every 5 minutes to transform the data.
Why it's wrong here
Batch processing adds latency and is not cost-effective for near-real-time.
✗
Use Amazon S3 Events to trigger a Lambda function whenever a new object is created.
Why it's wrong here
This would process files after they are stored, not before, and incurs additional S3 costs.
✓
Configure the Firehose delivery stream to invoke a Lambda function for data transformation.
Why this is correct
Firehose supports built-in Lambda transformation for real-time processing.
Related concept
CIDR notation defines the prefix length.

Common exam traps

Common exam trap: usable hosts are not the same as total addresses

Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.

Detailed technical explanation

How to think about this question

Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.

KKey Concepts to Remember

CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.

TExam Day Tips

Write the block size before choosing the subnet.
Check whether the question asks for hosts, subnets or a specific address range.
Do not confuse /24, /25, /26 and /27 host counts.

Key takeaway

Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.

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.

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

Got this wrong? Here's your next step.

Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DEA-C01 subnetting questions on CIDR, address ranges, and subnet selection.

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FAQ

Questions learners often ask

What does this DEA-C01 question test?

Data Ingestion and Transformation — This question tests Data Ingestion and Transformation — CIDR notation defines the prefix length..

What is the correct answer to this question?

The correct answer is: Configure the Firehose delivery stream to invoke a Lambda function for data transformation. — The most cost-effective way is to configure the Kinesis Data Firehose delivery stream to invoke an AWS Lambda function for data transformation before the data is delivered to S3. This approach is serverless and only runs when data is flowing, so you pay only for the compute time used during transformation. Option A (Athena CTAS) would require querying after storage, adding cost and latency. Option B (Glue batch job) runs on a schedule regardless of data volume, leading to idle costs, and introduces latency. Option C (S3 Events with Lambda) triggers after data is already stored, meaning the data is first stored in raw form, then transformed, doubling storage costs and adding complexity. Therefore, the Firehose-integrated Lambda is the most cost-effective and low-latency option.

What should I do if I get this DEA-C01 question wrong?

What is the key concept behind this question?

CIDR notation defines the prefix length.

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