The answer is to use pglogical replication from on-premises to RDS alongside AWS DMS with full load and Change Data Capture (CDC). This combination minimizes downtime because DMS first performs a full load of the existing data, then CDC continuously replicates ongoing changes in near real-time using PostgreSQL’s logical replication slots, ensuring the target stays synchronized until cutover. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of zero-downtime migration strategies and the interplay between native PostgreSQL tools and managed AWS services. A common trap is assuming DMS alone handles everything, but pglogical provides a more resilient, native replication layer that reduces latency and avoids schema conflicts. Remember the memory tip: “Full load first, CDC keeps it nursed—pglogical for the final burst.”
DBS-C01 Deployment and Migration Practice Question
This DBS-C01 practice question tests your understanding of deployment and migration. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 an on-premises PostgreSQL database to Amazon RDS for PostgreSQL. They need to minimize downtime and ensure data consistency. Which TWO methods can be used together to achieve this?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use AWS DMS with full load and CDC
AWS DMS with full load and Change Data Capture (CDC) enables a zero-downtime migration by first copying the existing data (full load) and then continuously replicating ongoing changes from the on-premises PostgreSQL source to the Amazon RDS for PostgreSQL target. This ensures data consistency because CDC captures transactions in near real-time using the PostgreSQL logical replication slot mechanism, allowing the target to stay synchronized until the cutover.
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.
✗
Take a file system snapshot and copy to Amazon EBS
Why it's wrong here
File system snapshots are not directly usable for RDS.
✗
Use pg_dump and pg_restore
Why it's wrong here
This is a one-time export/import, not ongoing replication.
✓
Use AWS DMS with full load and CDC
Why this is correct
DMS can replicate data continuously.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Export data to Amazon S3 and import using COPY
Why it's wrong here
This is a batch approach, not ongoing replication.
✓
Set up pglogical replication from on-premises to RDS
Why this is correct
pglogical provides logical replication to minimize downtime.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think pg_dump/restore (Option B) is sufficient for minimal downtime, but they overlook that it requires a consistent snapshot and cannot capture ongoing changes, whereas the correct answer combines a full load with CDC to achieve near-zero downtime.
Detailed technical explanation
How to think about this question
pglogical replication (Option E) is a PostgreSQL extension that uses logical decoding to replicate data changes in near real-time, making it suitable for minimizing downtime. When combined with AWS DMS, pglogical can be used as the CDC source plugin for DMS, leveraging the same underlying logical replication slots to stream WAL changes. In a real-world scenario, you might set up pglogical directly between on-premises and RDS for PostgreSQL to avoid DMS overhead, but DMS provides a managed service with built-in monitoring and retry logic, which is often preferred for production migrations.
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 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.
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: Use AWS DMS with full load and CDC — AWS DMS with full load and Change Data Capture (CDC) enables a zero-downtime migration by first copying the existing data (full load) and then continuously replicating ongoing changes from the on-premises PostgreSQL source to the Amazon RDS for PostgreSQL target. This ensures data consistency because CDC captures transactions in near real-time using the PostgreSQL logical replication slot mechanism, allowing the target to stay synchronized until the cutover.
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: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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