DBS-C01 Deployment and Migration Practice Question
A company has a 100 GB MySQL database on an EC2 instance. They want to migrate to Amazon RDS for MySQL with minimal downtime. They have set up replication from the source to the target using MySQL native replication. After enabling replication, the 'Seconds_Behind_Master' value is increasing. The source database is write-heavy. What should the team do to reduce replication lag?
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
✓
Increase the RDS instance size to a larger instance class.
The replication lag is increasing because the RDS instance is not powerful enough to apply changes from the write-heavy source as fast as they arrive. Increasing the RDS instance class (option C) provides more CPU and memory resources, allowing the replica to apply transactions more quickly and reduce lag. Option A (tuning the source) might help but is not the most direct solution if the target is the bottleneck. Option B (Multi-AZ) improves availability, not replication performance. Option D (AWS DMS) is an alternative migration tool but does not directly address lag in an existing native replication setup.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Tune the source database to reduce write load.
Why it's wrong here
Tuning the source database to reduce write load could decrease the rate of changes, but it does not directly address the target's ability to apply changes; the target is the bottleneck here, so this is not the best immediate fix.
- ✗
Enable Multi-AZ on the RDS instance.
Why it's wrong here
Multi-AZ on RDS provides a standby replica for high availability but does not improve the performance of applying replication changes on the primary instance.
- ✓
Increase the RDS instance size to a larger instance class.
Why this is correct
Increasing the RDS instance size gives more CPU and memory resources to the database, enabling it to apply replication changes faster and reduce the 'Seconds_Behind_Master' value.
- ✗
Switch to AWS DMS for migration.
Why it's wrong here
AWS DMS is a service for migrating databases with minimal downtime, but it does not help fix replication lag in an already-configured native replication setup.
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