Which solution would provide the HIGHEST availability?

Explanations:

While moving static assets to CloudFront and the database to RDS Multi-AZ improves availability of those components, keeping the application on EC2 in an Auto Scaling group does not provide thehighestlevel of availability. Auto Scaling will replace failed instances, but there will be a short period of downtime during replacement.

This option does not decouple the application and database tiers effectively. Placing both application and database on EC2 instances in an Auto Scaling group still means they are dependent on the same instances. If an instance fails, both application and database are affected. This does not provide high availability. Also, using a medium EC2 instance is likely a downgrade in performance.

Moving the application to Lambda is not suitable if the application has long-running processes. Lambda functions have execution time limits. Moving to DynamoDB is also not appropriate because the application currently uses MySQL, implying a relational data model that is not directly compatible with DynamoDB. This would require a significant application rewrite.

This is the solution that provides thehighestavailability. Moving static assets to S3 and using CloudFront provides global content delivery and high availability for static content. Using ECS with Auto Scaling distributes the application across multiple containers and Availability Zones, providing high availability and scalability. Moving the database to RDS with Multi-AZ provides database high availability. Decoupling all three tiers and using managed services with built-in high availability features results in the most resilient architecture.