DBS-C01 Monitoring and Troubleshooting Practice Question
A company has an Amazon Aurora MySQL DB cluster with one writer and two readers. The application is experiencing high read latency. CloudWatch shows that the 'AuroraBinlogReplicaLag' metric is high for one of the reader instances. What 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 reader instance is not keeping up with the write workload from the writer
The 'AuroraBinlogReplicaLag' metric measures the lag between the writer and a reader when using binary log replication. A high value indicates that the reader is not applying changes from the writer quickly enough, causing read latency. This is typically because the reader instance is not keeping up with the write workload from the writer. Option A is incorrect because Aurora storage is shared and not the cause of replication lag. Option C is incorrect; while an undersized reader can contribute to lag, the primary cause is the reader not keeping pace with writes, not necessarily size. Option D is incorrect because parameter groups affect settings but not replication 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 Aurora cluster storage is experiencing high I/O latency
Why it's wrong here
Aurora uses a shared storage volume, so all instances would be affected.
- ✓
The reader instance is not keeping up with the write workload from the writer
Why this is correct
Binlog replication lag means the reader is behind in applying changes.
- ✗
The reader instance is undersized and needs to be scaled up
Why it's wrong here
While undersizing could contribute, the direct symptom is replication lag.
- ✗
The DB cluster parameter group is misconfigured
Why it's wrong here
Parameter group misconfiguration would affect all instances.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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