The answer is to increase the DB instance class of the read replica. This directly reduces cross-region RDS MySQL read replica lag by providing the replica with more CPU and memory, enabling it to apply binary log (binlog) events from the primary faster than a smaller instance can. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding that cross-region replication lag is typically a bottleneck on the replica side, not the primary—so scaling the replica instance, rather than the primary, is the targeted fix. A common trap is to assume you must upgrade the primary or adjust network settings, but the lag is caused by the replica struggling to keep up with the write rate during peak hours. Memory tip: “Replica lag? Scale the replica, not the flag.”
DBS-C01 Management and Operations Practice Question
This DBS-C01 practice question tests your understanding of management and operations. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 using Amazon RDS for MySQL with a cross-Region read replica to support disaster recovery. The primary DB instance is in us-west-2, and the read replica is in us-east-1. The read replica is used for reporting and also serves as a failover target. The operations team notices that the read replica lag is consistently above 10 seconds during peak hours. What should the team do to reduce replica lag?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Increase the DB instance class of the read replica.
Increasing the DB instance class of the read replica provides more CPU and memory resources, which allows the replica to apply changes from the binary log more quickly. Cross-Region replication lag is often caused by the replica being unable to keep up with the write rate on the primary, so scaling up the replica directly addresses the bottleneck in applying binlog events.
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.
✓
Increase the DB instance class of the read replica.
Why this is correct
A larger instance class can process replication events faster.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable Multi-AZ on the primary DB instance.
Why it's wrong here
Multi-AZ provides high availability, not replication performance.
✗
Increase the backup retention period for the primary DB instance.
Disable binary logging (binlog) on the primary DB instance.
Why it's wrong here
Binary logging is required for replication.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think enabling Multi-AZ on the primary will reduce replica lag, but Multi-AZ only provides synchronous replication within the same Region and does not affect cross-Region asynchronous replication performance.
Detailed technical explanation
How to think about this question
Cross-Region replication in RDS for MySQL uses asynchronous binlog-based replication, where the primary writes events to its binary log and the replica reads and applies them. Lag can increase if the replica's instance class is undersized for the volume of writes, or if network latency between Regions is high. In some cases, using a larger instance class with enhanced networking can reduce the time to apply binlog events, especially for large transactions or DDL statements.
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.
Management and Operations — This question tests Management and Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Increase the DB instance class of the read replica. — Increasing the DB instance class of the read replica provides more CPU and memory resources, which allows the replica to apply changes from the binary log more quickly. Cross-Region replication lag is often caused by the replica being unable to keep up with the write rate on the primary, so scaling up the replica directly addresses the bottleneck in applying binlog events.
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: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
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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