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Data Operations and Support →hardMultiple ChoiceObjective-mapped

DEA-C01 Data Operations and Support Practice Question

This DEA-C01 practice question tests your understanding of data operations and support. 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.

Your company runs a data pipeline that ingests data from AWS Database Migration Service (DMS) into Amazon S3 in Parquet format. An AWS Glue ETL job then transforms the data and loads it into an Amazon Redshift cluster. The Glue job uses a JDBC connection to Redshift. Recently, the Glue job started failing with a 'communication failure' error when writing to Redshift. The Redshift cluster is in a VPC with public accessibility disabled. The Glue job runs in a VPC with a subnet that has a route to a NAT gateway. The security group for Redshift allows inbound traffic from the Glue job's security group. The Glue job's IAM role has the necessary permissions. What is the most likely cause?

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.

A
The Glue job's IAM role does not have the redshift:DescribeClusters permission.
Why wrong: The job uses a JDBC URL, not API calls; IAM permissions are for the Glue service role.
B
The Redshift cluster's public accessibility is disabled, but the Glue job is trying to connect over the internet.
Why wrong: The Glue job runs in a VPC and should use a private connection.
C
The Glue job and Redshift cluster are in different VPCs that are not peered or connected via VPC Transit Gateway.
Without VPC peering or transit gateway, the Glue job cannot reach the Redshift cluster.
D
The NAT gateway is not configured to allow traffic to the Redshift cluster's subnet.
Why wrong: NAT gateways are for internet traffic; Redshift is internal.

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

✓

The Glue job and Redshift cluster are in different VPCs that are not peered or connected via VPC Transit Gateway.

Option C is correct because even though the security group allows inbound traffic, the Glue job's VPC may not have a route to the Redshift cluster's VPC if they are in different VPCs. Option A is wrong because IAM permissions are not the issue. Option B is wrong because the Redshift cluster is in a VPC and not publicly accessible. Option D is wrong because the NAT gateway is for outbound internet, not for connecting to Redshift within the same VPC.

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.

✗
The Glue job's IAM role does not have the redshift:DescribeClusters permission.
Why it's wrong here
The job uses a JDBC URL, not API calls; IAM permissions are for the Glue service role.
✗
The Redshift cluster's public accessibility is disabled, but the Glue job is trying to connect over the internet.
Why it's wrong here
The Glue job runs in a VPC and should use a private connection.
✓
The Glue job and Redshift cluster are in different VPCs that are not peered or connected via VPC Transit Gateway.
Why this is correct
Without VPC peering or transit gateway, the Glue job cannot reach the Redshift cluster.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
CIDR notation defines the prefix length.
✗
The NAT gateway is not configured to allow traffic to the Redshift cluster's subnet.
Why it's wrong here
NAT gateways are for internet traffic; Redshift is internal.

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 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 Operations and Support — This question tests Data Operations and Support — CIDR notation defines the prefix length..

What is the correct answer to this question?

The correct answer is: The Glue job and Redshift cluster are in different VPCs that are not peered or connected via VPC Transit Gateway. — Option C is correct because even though the security group allows inbound traffic, the Glue job's VPC may not have a route to the Redshift cluster's VPC if they are in different VPCs. Option A is wrong because IAM permissions are not the issue. Option B is wrong because the Redshift cluster is in a VPC and not publicly accessible. Option D is wrong because the NAT gateway is for outbound internet, not for connecting to Redshift within the same VPC.

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

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?

CIDR notation defines the prefix length.

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