Which solution will meet these requirements?
Amazon DynamoDB
Amazon RDS for MySQL
MySQL-compatible Amazon Aurora Serverless
MySQL deployed on Amazon EC2 in an Auto Scaling group
Explanations:
Amazon DynamoDB is a NoSQL database service that requires significant changes to the application code and data model, which goes against the requirement of no database modifications.
Amazon RDS for MySQL is a managed relational database service but does not offer automatic scaling based on usage patterns, which may lead to cost inefficiencies during low usage periods.
MySQL-compatible Amazon Aurora Serverless automatically scales the database capacity based on application demand and is compatible with existing MySQL applications, requiring no database modifications.
Deploying MySQL on Amazon EC2 in an Auto Scaling group would require more management overhead and may not be cost-effective due to the need to manage the EC2 instances and potentially underutilized resources during low usage periods.