Explanation

AWS Lambda is the correct answer because:

• Serverless Architecture: AWS Lambda is a serverless compute service that automatically scales resources up or down based on the number of incoming requests or events
• Automatic Scaling: Lambda functions automatically scale from zero to thousands of parallel executions without any manual intervention
• No Operational Overhead: Unlike Amazon EC2 which requires manual configuration of Auto Scaling Groups, Lambda handles scaling automatically
• Event-Driven: Lambda scales in response to triggers from various AWS services like API Gateway, S3, DynamoDB, etc.

Why other options are incorrect:

• Amazon SQS: This is a message queuing service, not a compute service
• Amazon EC2: While EC2 can be made scalable using Auto Scaling Groups, it requires manual configuration and doesn't automatically scale by default
• Amazon Aurora: This is a managed relational database service, not a compute service

Lambda's automatic scaling makes it ideal for applications with variable or unpredictable workloads.