DBS-C01 Deployment and Migration Practice Question
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?
⚠ Common exam trap
A common mix-up: 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.
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.
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.
- ✗
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.
Go deeper
Related to this question
About these practice questions
One of 1,663 original DBS-C01 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.