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DBS-C01 Deployment and Migration Practice Question

This DBS-C01 practice question tests your understanding of deployment and migration. 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 startup is deploying a new web application on AWS. The application uses Amazon RDS for PostgreSQL as its database. The developers need to create the initial schema and load test data. They have a SQL script file that creates tables and inserts 10,000 rows. The DB instance is a db.t3.micro with 20 GB gp2 storage. The developers connect to the RDS instance using pgAdmin from their local machine and run the script. The script fails with a 'connection reset' error after inserting 5,000 rows. 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 DB instance ran out of memory or CPU credits due to the intensive script
Why wrong: Incorrect. A db.t3.micro has sufficient resources for a script inserting 10,000 rows; memory or CPU exhaustion is unlikely to cause a connection reset.
B
The max_connections parameter was set too low
Why wrong: Incorrect. The default max_connections for a db.t3.micro is sufficient for a single connection; a low max_connections would prevent new connections, not reset an existing one.
C
The storage volume reached its maximum capacity
Why wrong: Incorrect. 20 GB storage is more than enough for 10,000 rows of test data; storage exhaustion would produce a disk-full error, not a connection reset.
D
The security group blocked the connection due to a timeout
Correct. A security group can have timeout settings that cause the connection to be reset if the script runs longer than the timeout, which is a common issue with long-running queries through clients like pgAdmin.

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 security group blocked the connection due to a timeout

The most likely cause is that the connection was terminated by an idle timeout on an intermediate network component (such as a NAT Gateway, which has a default idle timeout of 350 seconds, or the client-side firewall/proxy). Security groups are stateful and do not have configurable timeout settings, so they are not directly responsible. The script's duration likely exceeded the idle timeout, causing a 'connection reset' error. Option A is unlikely because a db.t3.micro can handle inserting 10,000 rows without exhausting memory or CPU credits; the error is network-related, not resource-related. Option B is incorrect because max_connections is sufficient for a single connection. Option C is incorrect because 20 GB storage is far more than needed for 10,000 rows.

Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.

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 DB instance ran out of memory or CPU credits due to the intensive script
Why it's wrong here
Incorrect. A db.t3.micro has sufficient resources for a script inserting 10,000 rows; memory or CPU exhaustion is unlikely to cause a connection reset.
✗
The max_connections parameter was set too low
Why it's wrong here
Incorrect. The default max_connections for a db.t3.micro is sufficient for a single connection; a low max_connections would prevent new connections, not reset an existing one.
✗
The storage volume reached its maximum capacity
Why it's wrong here
Incorrect. 20 GB storage is more than enough for 10,000 rows of test data; storage exhaustion would produce a disk-full error, not a connection reset.
✓
The security group blocked the connection due to a timeout
Why this is correct
Correct. A security group can have timeout settings that cause the connection to be reset if the script runs longer than the timeout, which is a common issue with long-running queries through clients like pgAdmin.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.

Common exam traps

Common exam trap: NAT rules depend on direction and matching traffic

NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.

Detailed technical explanation

How to think about this question

NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.

KKey Concepts to Remember

Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.

TExam Day Tips

Identify inside and outside interfaces first.
Check whether the scenario needs static NAT, dynamic NAT or PAT.
Do not confuse NAT matching ACLs with normal packet-filtering intent.

Key takeaway

NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.

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 the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DBS-C01 NAT questions on configuration and troubleshooting.

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FAQ

Questions learners often ask

What does this DBS-C01 question test?

Deployment and Migration — This question tests Deployment and Migration — Static NAT maps one inside address to one outside address..

What is the correct answer to this question?

The correct answer is: The security group blocked the connection due to a timeout — The most likely cause is that the connection was terminated by an idle timeout on an intermediate network component (such as a NAT Gateway, which has a default idle timeout of 350 seconds, or the client-side firewall/proxy). Security groups are stateful and do not have configurable timeout settings, so they are not directly responsible. The script's duration likely exceeded the idle timeout, causing a 'connection reset' error. Option A is unlikely because a db.t3.micro can handle inserting 10,000 rows without exhausting memory or CPU credits; the error is network-related, not resource-related. Option B is incorrect because max_connections is sufficient for a single connection. Option C is incorrect because 20 GB storage is far more than needed for 10,000 rows.

What should I do if I get this DBS-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?

Static NAT maps one inside address to one outside address.

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