The answer is to increase the instance size of the read replica. This directly addresses the root cause of RDS MySQL read replica lag: the replica’s hardware is overwhelmed by the rate of change logs arriving from the primary, which handles 5000 writes per second. By scaling up the replica’s compute and memory resources, it can apply binary log events faster, thereby closing the replication gap. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding that replica lag is typically a bottleneck on the replica side, not the primary—a common trap is to suggest disabling binary logging or adding Multi-AZ, both of which break replication or improve availability, not throughput. Remember the key insight: when reducing read replica lag, always look to the replica’s capacity first. A useful memory tip is “lag is on the laggard”—the slowest component in the replication chain is the one that needs scaling.
DBS-C01 Monitoring and Troubleshooting Practice Question
This DBS-C01 practice question tests your understanding of monitoring and troubleshooting. 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 development team is using Amazon RDS for MySQL with read replicas to offload reporting queries. They notice that the read replica is consistently lagging behind the primary by several seconds. The primary handles 5000 writes per second. Which action would most likely reduce replica lag?
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.
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 instance size of the read replica.
Option D is correct because increasing the replica instance size can improve its ability to apply changes faster. Option A is incorrect because disabling binary logging would break replication. Option B is incorrect because the replica lag is due to the replica not keeping up, not the primary. Option C is incorrect because Multi-AZ is for high availability, not for reducing replica lag.
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 'max_connections' parameter on the primary instance.
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Identify which DBS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Monitoring and Troubleshooting — This question tests Monitoring and Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Increase the instance size of the read replica. — Option D is correct because increasing the replica instance size can improve its ability to apply changes faster. Option A is incorrect because disabling binary logging would break replication. Option B is incorrect because the replica lag is due to the replica not keeping up, not the primary. Option C is incorrect because Multi-AZ is for high availability, not for reducing replica lag.
What should I do if I get this DBS-C01 question wrong?
Identify which DBS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely", "primary". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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