A web application runs on Amazon EC2 instances in a single Availability Zone and stores its data in a Single-AZ Amazon RDS for MySQL DB instance. The company wants the application to keep working if that Availability Zone fails. Which two changes meet this requirement? (Choose two.)
Choose two.
Show answer and explanation
Answer: A and B
Surviving the loss of an Availability Zone requires removing every single-AZ dependency from the architecture. Running the EC2 fleet in an Auto Scaling group that spans at least two AZs behind the load balancer keeps the surviving AZ serving traffic while the ASG replaces the instances that were lost.
Converting the database to an RDS Multi-AZ deployment puts a synchronous standby in a different AZ and fails over to it automatically, so the connection endpoint stays the same and the application continues without changes.
Why the other options are wrong
- C. A read replica placed in the same Availability Zone fails together with the primary, and even a healthy replica never takes over traffic on its own.
- D. EBS snapshots exist to recover data after a failure; restoring from them doesn't keep the application running during the outage.
- E. A larger instance type adds capacity, not redundancy — everything is still in that one Availability Zone.
Exam tip. "Keep working if an AZ fails" is high availability: Multi-AZ everywhere. Backups and snapshots answer recovery questions, not availability ones.