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Question 651 of 1,730

Deployment and Migration →easyMultiple ChoiceObjective-mapped

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 company is migrating a PostgreSQL database to Amazon Aurora PostgreSQL. To minimize downtime, they plan to use the AWS DMS with change data capture (CDC). During the full load phase, DMS reports an error: 'Failed to add foreign key constraint'. 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.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.

A
CDC is incompatible with foreign key constraints
Why wrong: CDC works with constraints; the error occurs during full load, not CDC.
B
Referential integrity violations in the source data
DMS applies constraints after loading data, and if data violates them, the task fails.
C
The target table lacks a primary key
Why wrong: DMS can create tables without primary keys during full load.
D
Data type mismatch between source and target
Why wrong: DMS handles data type conversions and would report a different error.

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

✓

Referential integrity violations in the source data

The error 'Failed to add foreign key constraint' during the full load phase of AWS DMS indicates that the source data contains referential integrity violations. DMS attempts to apply foreign key constraints on the target Aurora PostgreSQL after loading data, but if parent-child relationships are broken (e.g., orphan rows), the constraint creation fails. This is a common issue when migrating databases with existing data integrity problems, as DMS does not automatically validate or fix source data.

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.

✗
CDC is incompatible with foreign key constraints
Why it's wrong here
CDC works with constraints; the error occurs during full load, not CDC.
✓
Referential integrity violations in the source data
Why this is correct
DMS applies constraints after loading data, and if data violates them, the task fails.
Clue confirmation
The clue words "most likely", "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The target table lacks a primary key
Why it's wrong here
DMS can create tables without primary keys during full load.
✗
Data type mismatch between source and target
Why it's wrong here
DMS handles data type conversions and would report a different error.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates assume the error is due to a DMS limitation or configuration issue, rather than recognizing it as a data integrity problem in the source database that must be resolved before migration.

Detailed technical explanation

How to think about this question

AWS DMS uses a two-phase migration: full load (bulk copy) followed by CDC. During full load, DMS disables foreign key constraints on the target to speed up data insertion, then re-enables them after the load. If the source has orphan rows (e.g., a child row referencing a non-existent parent), the constraint creation fails. This is often due to deferred constraint checking in the source database (e.g., PostgreSQL's DEFERRABLE constraints) or application-level integrity gaps. In real-world scenarios, running a pre-migration validation script to check for orphaned records can prevent this error.

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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.

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 DBS-C01 question test?

Deployment and Migration — This question tests Deployment and Migration — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Referential integrity violations in the source data — The error 'Failed to add foreign key constraint' during the full load phase of AWS DMS indicates that the source data contains referential integrity violations. DMS attempts to apply foreign key constraints on the target Aurora PostgreSQL after loading data, but if parent-child relationships are broken (e.g., orphan rows), the constraint creation fails. This is a common issue when migrating databases with existing data integrity problems, as DMS does not automatically validate or fix source data.

What should I do if I get this DBS-C01 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: "most likely", "minimum / minimize". 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?

Read the scenario before looking for a memorised answer.

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This DBS-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 DBS-C01 exam.