DBS-C01 Monitoring and Troubleshooting Practice Question
A company is running an Amazon Aurora MySQL-Compatible DB cluster. The application is experiencing increased latency during peak hours. The DB cluster's CPU utilization is at 40%, but the ReadReplicaLag metric is high. Which of the following is the most likely cause?
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 writer instance is experiencing I/O bottlenecks, causing slow replication
High replica lag indicates the replica is falling behind, often due to insufficient I/O capacity on the writer or replica. Option B is wrong because read replicas handle SELECT queries. Option C is wrong because the DB cluster parameter group is shared and misconfiguration is not the most likely cause for high replica lag. Option D is wrong because binary log retention period does not affect replica lag directly.
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 writer instance is experiencing I/O bottlenecks, causing slow replication
Why this is correct
I/O bottlenecks on the writer can delay writing to the binary log, increasing replica lag.
- ✗
The read replica is receiving too many write requests
Why it's wrong here
Read replicas do not accept write requests in Aurora.
- ✗
The DB cluster parameter group is misconfigured
Why it's wrong here
Parameter group misconfiguration is less likely to cause replica lag.
- ✗
The binary log retention period is too long
Why it's wrong here
Binary log retention does not cause replica lag.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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