SOA-C02 Reliability and Business Continuity Practice Question
A company runs a production application on EC2 instances in an Auto Scaling group behind an Application Load Balancer. The application uses an RDS for PostgreSQL database. The SysOps administrator has configured a read replica in a different AWS Region for disaster recovery. During a disaster, the primary region becomes unavailable. The administrator promotes the read replica to a standalone instance. After promoting, the application fails to connect to the new database because the endpoint changed. The administrator needs to minimize downtime. What should the administrator do to handle the endpoint change automatically?
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 Amazon Route 53 with a weighted alias record that points to the primary database endpoint, and configure a health check to fail over to the secondary endpoint.
By using Amazon Route 53 with a weighted alias record that points to the primary database endpoint and configuring a health check, the administrator can automate DNS failover. When the primary region becomes unavailable, the health check fails, and Route 53 automatically routes traffic to the secondary record that points to the promoted read replica's endpoint. This minimizes downtime. Option A is wrong because Elastic IP addresses cannot be assigned to RDS instances; they are used for EC2 instances. Option C is wrong because manually updating application configuration files would increase downtime and is not automatic. Option D is wrong because an RDS proxy does not automatically update the endpoint after a disaster recovery promotion; it still requires the endpoint to be changed in the application configuration.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Assign an Elastic IP address to the RDS instance.
Why it's wrong here
Elastic IP addresses cannot be attached to RDS instances; they are only valid for EC2-classic or VPC resources like EC2 instances and NAT gateways. RDS exposes a DNS endpoint that automatically changes when a failover occurs, and there is no mechanism to pin a static IP to an RDS DB instance. Therefore, this approach does not provide reliable failover handling and would leave the application unable to reconnect after a database failure.
- ✓
Use Amazon Route 53 with a weighted alias record that points to the primary database endpoint, and configure a health check to fail over to the secondary endpoint.
Why this is correct
Route 53 weighted alias records can point to the RDS primary and secondary endpoints, allowing you to control traffic distribution. By associating a health check with the primary record, Route 53 automatically removes the primary from DNS resolution when the health check fails, causing traffic to be sent to the secondary endpoint. This achieves automated failover with minimal downtime, and the application continues using the same DNS name throughout.
- ✗
Update the application configuration files to point to the new endpoint.
Why it's wrong here
Manually changing the application's connection string to reference the promoted replica requires you to detect the failure, edit configuration files, and redeploy or restart the application. This process is slow, error-prone, and results in extended downtime, which is unacceptable for a production database failover. Unlike a DNS-based solution, it does not provide any automated detection or traffic rerouting.
- ✗
Use an RDS proxy and configure it to automatically failover to the promoted replica.
Why it's wrong here
RDS Proxy acts as a connection broker, but it still points to a specific RDS endpoint and does not automatically know which replica to use after a manual promotion. To use the proxy with the promoted replica, you would need to reconfigure the proxy target group or endpoint, which is a manual step. Therefore, it does not eliminate the need for intervention and does not provide automatic failover to a secondary database on its own.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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