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Data Engineering →mediumMultiple ChoiceObjective-mapped

MLS-C01 Data Engineering Practice Question

This MLS-C01 practice question tests your understanding of data engineering. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 AWS Glue to run ETL jobs that transform data from Amazon S3 to Amazon Redshift. The Glue job writes data to Redshift using the JDBC connection. Recently, the job has been failing with connection timeout errors when writing to Redshift. The Redshift cluster is a 2-node dc2.large cluster. The Glue job processes about 50 GB of data per run. The errors occur sporadically, and the job succeeds after a few retries. The data engineer needs to resolve the issue to prevent job failures. What should the engineer do?

A
Increase the Redshift cluster size to 4 nodes.
Why wrong: Scaling Redshift may help but does not address the JDBC driver inefficiency.
B
Modify the Glue job to write data to S3 first, then use the Redshift COPY command to load data.
Using COPY from S3 is the recommended approach for bulk loading into Redshift; it is faster and more reliable than JDBC writes.
C
Increase the Glue job timeout to 24 hours.
Why wrong: Longer timeout will not fix the underlying connection issue.
D
Use AWS Database Migration Service (DMS) to load data into Redshift.
Why wrong: DMS is for ongoing replication, not for ETL jobs.

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

✓

Modify the Glue job to write data to S3 first, then use the Redshift COPY command to load data.

The correct answer is B. Writing to Redshift via JDBC is inefficient for large volumes and prone to timeouts. The recommended approach is to write data to S3 first and then use the Redshift COPY command, which is optimized for bulk loading and more reliable. Option A is incorrect because increasing the cluster size addresses capacity but not the inherent inefficiency of JDBC writes. Option C is incorrect because increasing the timeout only masks the issue without resolving the underlying problem. Option D is incorrect because AWS DMS is designed for database migration, not for ETL job processing within Glue.

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.

✗
Increase the Redshift cluster size to 4 nodes.
Why it's wrong here
Scaling Redshift may help but does not address the JDBC driver inefficiency.
✓
Modify the Glue job to write data to S3 first, then use the Redshift COPY command to load data.
Why this is correct
Using COPY from S3 is the recommended approach for bulk loading into Redshift; it is faster and more reliable than JDBC writes.
Related concept
CIDR notation defines the prefix length.
✗
Increase the Glue job timeout to 24 hours.
Why it's wrong here
Longer timeout will not fix the underlying connection issue.
✗
Use AWS Database Migration Service (DMS) to load data into Redshift.
Why it's wrong here
DMS is for ongoing replication, not for ETL jobs.

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 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.

Visual reference

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 MLS-C01 subnetting questions on CIDR, address ranges, and subnet selection.

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FAQ

Questions learners often ask

What does this MLS-C01 question test?

Data Engineering — This question tests Data Engineering — CIDR notation defines the prefix length..

What is the correct answer to this question?

The correct answer is: Modify the Glue job to write data to S3 first, then use the Redshift COPY command to load data. — The correct answer is B. Writing to Redshift via JDBC is inefficient for large volumes and prone to timeouts. The recommended approach is to write data to S3 first and then use the Redshift COPY command, which is optimized for bulk loading and more reliable. Option A is incorrect because increasing the cluster size addresses capacity but not the inherent inefficiency of JDBC writes. Option C is incorrect because increasing the timeout only masks the issue without resolving the underlying problem. Option D is incorrect because AWS DMS is designed for database migration, not for ETL job processing within Glue.

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

What is the key concept behind this question?

CIDR notation defines the prefix length.

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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.