AWS Certified Solutions Architect – Professional (SAP-C02) — Question 355

A live-events company is designing a scaling solution for its ticket application on AWS. The application has high peaks of utilization during sale events. Each sale event is a one-time event that is scheduled. The application runs on Amazon EC2 instances that are in an Auto Scaling group. The application uses PostgreSQL for the database layer.

The company needs a scaling solution to maximize availability during the sale events.

Which solution will meet these requirements?

Answer options

• A. Use a predictive scaling policy for the EC2 instances. Host the database on an Amazon Aurora PostgreSQL Serverless v2 Multi-AZ DB instance with automatically scaling read replicas. Create an AWS Step Functions state machine to run parallel AWS Lambda functions to pre-warm the database before a sale event. Create an Amazon EventBridge rule to invoke the state machine.
• B. Use a scheduled scaling policy for the EC2 instances. Host the database on an Amazon RDS for PostgreSQL Mulli-AZ DB instance with automatically scaling read replicas. Create an Amazon EventBridge rule that invokes an AWS Lambda function to create a larger read replica before a sale event. Fail over to the larger read replica. Create another EventBridge rule that invokes another Lambda function to scale down the read replica after the sale event.
• C. Use a predictive scaling policy for the EC2 instances. Host the database on an Amazon RDS for PostgreSQL MultiAZ DB instance with automatically scaling read replicas. Create an AWS Step Functions state machine to run parallel AWS Lambda functions to pre-warm the database before a sale event. Create an Amazon EventBridge rule to invoke the state machine.
• D. Use a scheduled scaling policy for the EC2 instances. Host the database on an Amazon Aurora PostgreSQL Multi-AZ DB cluster. Create an Amazon EventBridge rule that invokes an AWS Lambda function to create a larger Aurora Replica before a sale event. Fail over to the larger Aurora Replica. Create another EventBridge rule that invokes another Lambda function to scale down the Aurora Replica after the sale event.

Correct answer: D

Explanation

Scheduled scaling is the most appropriate strategy for EC2 instances here because the sale events are planned, one-time occurrences, whereas predictive scaling requires recurring historical patterns to function effectively. Amazon Aurora PostgreSQL is preferred over Amazon RDS for PostgreSQL because Aurora supports extremely fast, low-latency failover to a larger replica without the storage-coupling limitations of RDS. Using EventBridge and Lambda to scale up the Aurora replica and failover before the event ensures the primary database can handle the sudden peak load with minimal disruption.