DBS-C01 Management and Operations Practice Question
Network Topology
A database administrator runs the above AWS CLI command to troubleshoot replication issues. The DB instance 'mydb' is a read replica of 'my-source-db'. The administrator notices that the replica lag is increasing. Which of the following is the MOST likely cause?
⚠ Common exam trap
Candidates often assume instance size (Option C) is the primary cause of replica lag, but the question explicitly mentions a cross-Region scenario (implied by the AWS CLI command targeting a different Region), making network latency the most likely culprit over compute capacity.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The read replica is in a different AWS Region than the source.
When a read replica is in a different AWS Region than the source, the replication traffic must traverse the public internet or a VPN connection, introducing network latency and potential bandwidth constraints. This cross-region lag is a common cause of increasing replica lag, as the asynchronous MySQL replication relies on a single I/O thread to download the binary log events from the source, and any network delay directly impacts the replica's ability to keep up.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The source DB instance is running a different MySQL version.
Why it's wrong here
The version is the same.
- ✗
The read replica has Multi-AZ disabled.
Why it's wrong here
Multi-AZ on a replica does not affect replication lag.
- ✗
The read replica is using a smaller instance class than the source.
Why it's wrong here
The instance class is not specified as smaller; it's db.r5.large.
- ✓
The read replica is in a different AWS Region than the source.
Why this is correct
Cross-Region replication introduces network latency, causing lag.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.