DBS-C01 Deployment and Migration Practice Question
A company is deploying a new Amazon RDS for SQL Server DB instance with Multi-AZ. The database will be used by a critical application that requires minimal downtime during failover. The application uses a single connection string with the CNAME of the RDS endpoint. During a recent failover test, the application experienced a 3-minute timeout. The DBA wants to reduce the failover time. The current RDS instance is db.r5.large with 100 GB gp2 storage. The application is hosted on EC2 in the same VPC. Which change would MOST effectively reduce the failover time?
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
✓
Configure the application to use a low TTL for DNS lookups and implement connection retries
The most effective because the 3-minute timeout during failover is likely due to DNS caching on the application side. By configuring the application to use a low TTL (e.g., 5 seconds) for DNS lookups and implementing connection retries with exponential backoff, the application can quickly resolve the new RDS endpoint's IP address after failover and re-establish connectivity promptly. Option A is incorrect because changing to Provisioned IOPS (io1) improves storage performance but does not reduce DNS-related failover time. Option B is incorrect because increasing the instance size does not directly impact failover duration. Option D is incorrect because Multi-AZ already provides automatic failover; a read replica with manual promotion would not reduce failover time and would require additional management.
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 storage to Provisioned IOPS (io1)
Why it's wrong here
Storage type does not affect Multi-AZ failover time.
- ✗
Change the instance type to db.r5.xlarge
Why it's wrong here
Larger instance size does not reduce failover time.
- ✓
Configure the application to use a low TTL for DNS lookups and implement connection retries
Why this is correct
Low TTL ensures the DNS record is refreshed quickly, reducing failover time.
- ✗
Use a read replica with automatic failover
Why it's wrong here
Read replicas are for read scaling, not automatic failover.
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