How Can You Confirm PostgreSQL Is Causing DMS CDC Latency?
A company needs to send customer call data from its on-premises PostgreSQL database to AWS to generate near real-time insights. The solution must capture and load updates from operational data stores that run in the PostgreSQL database. The data changes continuously. A data engineer configures an AWS Database Migration Service (AWS DMS) ongoing replication task. The task reads changes in near real time from the PostgreSQL source database transaction logs for each table. The task then sends the data to an Amazon Redshift cluster for processing. The data engineer discovers latency issues during the change data capture (CDC) of the task. The data engineer thinks that the PostgreSQL source database is causing the high latency. Which solution will confirm that the PostgreSQL database is the source of the high latency?
Community Votes
100% of anonymous learners picked answer D. Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
It tests the distinction between source-side CDC read latency and target-side backlog; the trap is choosing CDCIncomingChanges, which reflects queued changes rather than time spent reading PostgreSQL transaction logs.
This question tests how to isolate change data capture latency in an AWS DMS ongoing replication task from PostgreSQL to Amazon Redshift. The page establishes that CDCLatencySource, not CDCIncomingChanges or endpoint logs, confirms whether the PostgreSQL source is causing the delay.
Many learners choose CDCIncomingChanges (A) because it sounds like incoming changes from the source, but that metric tracks change events waiting to be applied and does not isolate PostgreSQL source read latency.
Community Discussion (3 comments)
Comments & Corrections
No comments yet — spotted an error or have a note? Share it below.
Expert Analysis
Why the Answer Is Correct
CDCLatencySource measures the time between reading a change from the PostgreSQL source transaction logs and the AWS DMS task receiving it, so an elevated value points specifically at source-side capture. Amazon CloudWatch is the supported monitoring surface for DMS task metrics, making CDCLatencySource a direct, non-invasive diagnostic. In an ongoing replication task with continuous changes, this metric separates source read delay from Redshift target apply delay. As tgv notes, "This metric measures the latency between the source database and the DMS task."Why the Other Options Are Wrong
CDCIncomingChanges (A) shows change events waiting to be applied, so a high value can result from a Redshift bottleneck rather than PostgreSQL capture delay. Verifying logical replication in postgresql.conf (B) is a prerequisite check: if logical replication were not configured, CDC would fail outright, but this does not confirm the source of measured latency. Enabling CloudWatch Logs for the source endpoint (C) may reveal connection or permission errors, but logs do not quantify source-side CDC latency, and an absence of errors does not prove the PostgreSQL database is the bottleneck.Community Comment Notes
Community consensus is unanimous for D. tgv links the official DMS monitoring metrics page and explains the source-to-task meaning, while sdas1 links the latency troubleshooting page and summarizes that a high CDCLatencySource indicates delayed source capture. HunkyBunky adds that "only D makes sense." No comment defends A, B, or C as a way to confirm PostgreSQL source latency.Official Reference
Exam Strategy
For DMS CDC latency questions, first decide whether the delay is on the source read side or target apply side, then map that to CDCLatencySource or CDCLatencyTarget. Do not pick configuration checks or endpoint logs when the question asks which metric confirms the source of latency.
Frequently Asked Questions
Why does CDCIncomingChanges not confirm PostgreSQL source latency?
CDCIncomingChanges reflects change events waiting to be applied, so it can rise from Redshift target bottlenecks; it does not measure time spent reading PostgreSQL transaction logs.
What does a high CDCLatencySource value mean in an AWS DMS CDC task?
It means changes are waiting between the PostgreSQL source and the DMS task, indicating source-side capture delay rather than Redshift apply latency.
Related Analysis
Practice All DEA-C01 Questions
Access 100 questions with complete answers and detailed explanations.
View Full DEA-C01 Practice Test →