The answer is AWS Database Migration Service (DMS) with ongoing replication, because this scenario requires minimal downtime PostgreSQL migration to RDS using DMS CDC. DMS captures ongoing changes from the source database’s transaction logs—specifically PostgreSQL’s Write-Ahead Log (WAL)—and continuously applies them to the target RDS instance, allowing the initial 500 GB load to complete while keeping both databases synchronized. This enables a near-zero-duration cutover, as you only need to stop writes on the source and promote the target. On the AWS Certified Database Specialty DBS-C01 exam, this question tests your understanding of change data capture (CDC) as a core requirement for low-downtime migrations; a common trap is choosing a full-load-only service, which cannot support ongoing replication and forces extended downtime during the final sync. Remember the memory tip: “DMS with CDC = WAL for zero downtime.”
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 500 GB on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The migration must have minimal downtime and support ongoing replication after the initial load. Which AWS service should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
AWS Database Migration Service (DMS) with ongoing replication
AWS Database Migration Service (DMS) with ongoing replication (change data capture, CDC) is required because the scenario demands minimal downtime and continuous synchronization after the initial 500 GB load. DMS uses transaction logs (e.g., PostgreSQL WAL) to capture and apply ongoing changes, enabling a near-zero-duration cutover. Full load only (Option B) would cause downtime during the final sync and cannot support ongoing replication.
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.
✗
AWS Schema Conversion Tool (SCT)
Why it's wrong here
SCT converts schema but does not handle data migration or replication.
✗
AWS Database Migration Service (DMS) with full load only
Why it's wrong here
Full load only causes downtime; CDC is needed for ongoing replication.
✓
AWS Database Migration Service (DMS) with ongoing replication
Why this is correct
DMS supports full load plus CDC for minimal downtime.
Related concept
Read the scenario before looking for a memorised answer.
✗
AWS Glue
Why it's wrong here
Glue is for ETL, not live database migration with replication.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'full load only' with 'full load + CDC' and overlook the requirement for ongoing replication, or they mistakenly think AWS SCT handles data migration when it only handles schema conversion.
Detailed technical explanation
How to think about this question
DMS ongoing replication uses the PostgreSQL logical replication slot to read the write-ahead log (WAL) in near real-time, applying changes to the target without locking the source. The initial 500 GB load is performed as a full LOB or bulk copy, after which CDC continuously streams DML and DDL changes. In a real-world scenario, you would also need to enable `rds.logical_replication` on the source RDS instance and ensure the WAL retention period is sufficient to avoid lag.
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.
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: AWS Database Migration Service (DMS) with ongoing replication — AWS Database Migration Service (DMS) with ongoing replication (change data capture, CDC) is required because the scenario demands minimal downtime and continuous synchronization after the initial 500 GB load. DMS uses transaction logs (e.g., PostgreSQL WAL) to capture and apply ongoing changes, enabling a near-zero-duration cutover. Full load only (Option B) would cause downtime during the final sync and cannot support ongoing replication.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is migrating a 500 GB on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The migration must have minimal downtime and support ongoing replication after the initial load. The network link has limited bandwidth, and the company wants to avoid costly data transfer fees. Which approach should be used?
medium
✓ A.Use AWS DMS with ongoing replication (CDC) from the start.
B.Use AWS Database Migration Service (DMS) with a full load only, then cut over.
C.Use pg_dump to export the database and pg_restore to import into RDS.
D.Use AWS Snowball Edge to transfer the database files, then load into RDS.
Why A: AWS DMS with ongoing replication (CDC) enables a full load followed by continuous change data capture, which meets the requirements of minimal downtime and ongoing replication. DMS compresses data in transit and can throttle network usage, helping to manage limited bandwidth and avoid costly data transfer fees by using the existing network link efficiently.
Variation 2. A company is migrating a 2 TB on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The migration must have minimal downtime and support ongoing replication. Which AWS service should be used?
medium
✓ A.AWS DMS
B.AWS Snowball Edge
C.AWS S3
D.RDS native PostgreSQL logical replication
Why A: Option C is correct because AWS Database Migration Service (DMS) supports ongoing replication from on-premises to RDS with minimal downtime. Option A is wrong because S3 is for storage, not database migration. Option B is wrong because Snowball is for large data transfer, not ongoing replication. Option D is wrong because RDS does not support native pglogical replication from on-premises easily.
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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.
Question Discussion
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