The answer is that the source PostgreSQL version must be 9.4 or later, and pglogical must be loaded into the shared_preload_libraries on the source instance. This is correct because pglogical operates as a background worker process that must be initialized at server start; without adding it to shared_preload_libraries, the extension cannot be installed or function, and the database must be restarted for the change to take effect. On the AWS Certified Database Specialty DBS-C01 exam, this prerequisite tests your understanding that logical replication extensions require server-level configuration, not just a database-level CREATE EXTENSION—a common trap is assuming you can skip the preload step. For pglogical prerequisites for logical replication from PostgreSQL to Aurora, remember that the extension must be “preloaded” before it can be “loaded.” Memory tip: think “preload before you load” to avoid missing the restart requirement.
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 self-managed PostgreSQL database to Amazon Aurora PostgreSQL. They want to use the pglogical extension for logical replication to minimize downtime. Which THREE prerequisites must be met before setting up pglogical?
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
✓
Add pglogical to shared_preload_libraries and restart the source database
Option A is correct because pglogical must be loaded into the shared preload libraries on the source PostgreSQL instance so that it is available at server start. Without this, the extension cannot be installed or used. The database must be restarted after modifying shared_preload_libraries for the change to take effect.
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.
✓
Add pglogical to shared_preload_libraries and restart the source database
Why this is correct
The extension must be loaded.
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.
✓
Set wal_level to logical in the source PostgreSQL configuration
Why this is correct
Logical replication requires wal_level=logical.
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.
✗
Configure max_wal_senders to at least 10
Why it's wrong here
Not a specific prerequisite for pglogical.
✗
Enable track_commit_timestamp on the source
Why it's wrong here
Not required for pglogical.
✓
Ensure the source PostgreSQL version is 9.4 or later
Why this is correct
pglogical supports PostgreSQL 9.4+.
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 confuse the prerequisites for pglogical with those for native PostgreSQL logical replication, which also requires max_replication_slots and max_wal_senders to be set, but pglogical does not mandate a specific value like 10 for max_wal_senders.
Detailed technical explanation
How to think about this question
pglogical uses logical replication slots to capture changes from the WAL, which requires wal_level=logical to include the necessary information for decoding. The shared_preload_libraries parameter ensures the pglogical extension's shared library is loaded at database startup, enabling the background worker processes that manage replication. In a real-world migration, failing to restart the source after setting shared_preload_libraries will result in the extension not being available, causing the setup to fail.
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: Add pglogical to shared_preload_libraries and restart the source database — Option A is correct because pglogical must be loaded into the shared preload libraries on the source PostgreSQL instance so that it is available at server start. Without this, the extension cannot be installed or used. The database must be restarted after modifying shared_preload_libraries for the change to take effect.
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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