DBS-C01 Deployment and Migration Practice Question
Network Topology
A company has an Aurora MySQL cluster with three instances. The current writer instance is 'mycluster-instance-1'. The company wants to failover to 'mycluster-instance-2' for maintenance. What is the most direct way to achieve this?
⚠ Common exam trap
Watch out — candidates often confuse rebooting an instance with triggering a failover, or assume that modifying an instance's settings can promote it, when in fact only the cluster-level failover command can explicitly designate a target replica as the new writer.
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
✓
Use the AWS CLI: aws rds failover-db-cluster --db-cluster-identifier mycluster --target-db-instance-identifier mycluster-instance-2
The AWS CLI command `aws rds failover-db-cluster` with the `--target-db-instance-identifier` parameter allows you to explicitly specify which Aurora replica should become the new writer instance. This is the most direct and supported method to initiate a controlled failover to 'mycluster-instance-2' without rebooting the current writer or manually modifying endpoints.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Change the cluster's endpoint to point to instance-2.
Why it's wrong here
Cluster endpoints are managed by RDS; you cannot manually redirect them.
- ✗
Modify 'mycluster-instance-2' to promote it to writer.
Why it's wrong here
There is no modify action to promote an instance; failover is required.
- ✗
Reboot 'mycluster-instance-1' to trigger a failover.
Why it's wrong here
Rebooting the writer causes a failover but does not guarantee instance-2 becomes the writer.
- ✓
Use the AWS CLI: aws rds failover-db-cluster --db-cluster-identifier mycluster --target-db-instance-identifier mycluster-instance-2
Why this is correct
This command initiates failover to the specified instance.
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