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 a PostgreSQL database to Amazon Aurora PostgreSQL. They have set up AWS DMS with change data capture (CDC). However, after the initial load, the CDC replication is experiencing high latency. 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.
The target Aurora instance has insufficient storage.
Why wrong: Storage issues cause errors, not latency.
The DMS instance is using an older engine version.
Why wrong: Version is unlikely cause.
The source database has large transactions that are not committed quickly.
Large uncommitted transactions delay CDC.
The network bandwidth is too low.
Why wrong: Network affects all phases equally.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The source database has large transactions that are not committed quickly.
Large uncommitted transactions on the source database cause DMS CDC to buffer changes until the transaction commits, leading to high latency. DMS must wait for the commit record before applying changes to the target Aurora instance, and during this time, CDC replication stalls, accumulating a backlog of changes.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The target Aurora instance has insufficient storage.
Why it's wrong here
Storage issues cause errors, not latency.
The DMS instance is using an older engine version.
Why it's wrong here
Version is unlikely cause.
The source database has large transactions that are not committed quickly.
Why this is correct
Large uncommitted transactions delay CDC.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
The network bandwidth is too low.
Why it's wrong here
Network affects all phases equally.
Common exam traps
The trap here is that candidates often assume network or infrastructure issues (like bandwidth or storage) are the primary cause of CDC latency, overlooking the fundamental constraint that DMS must wait for transaction commits before applying changes.
Detailed technical explanation
DMS CDC uses transaction logs (e.g., PostgreSQL WAL) to capture changes, but it cannot apply partial transactions to the target; it must buffer all changes from a transaction until the commit log record is read. This means a single large uncommitted transaction (e.g., an UPDATE affecting millions of rows) blocks the replication stream, causing latency to spike. In practice, splitting large transactions into smaller batches or tuning the source database's transaction commit frequency can mitigate this issue.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Deployment and Migration — This question tests Deployment and Migration — Read the scenario before looking for a memorised answer..
The correct answer is: The source database has large transactions that are not committed quickly. — Large uncommitted transactions on the source database cause DMS CDC to buffer changes until the transaction commits, leading to high latency. DMS must wait for the commit record before applying changes to the target Aurora instance, and during this time, CDC replication stalls, accumulating a backlog of changes.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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.
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