A company will move a multi-tier application to AWS to improve performance. Tiers communicate via RESTful services and transactions are dropped when a tier is overloaded. The solutions architect must design a solution that resolves dropped transactions and modernizes the application, with the highest operational efficiency. Which solution meets these requirements?

The correct solution leverages serverless technologies for high operational efficiency and scalability. Amazon API Gateway provides a managed entry point for RESTful services, handling traffic management and security. AWS Lambda functions offer a scalable, pay-per-execution compute environment for the application layer, eliminating the need to manage servers. Amazon SQS acts as a buffer between services, decoupling components and preventing dropped transactions by queuing requests during peak loads, ensuring messages are processed reliably. Incorrect options: Increasing EC2 instance size based on historical data is a reactive, less efficient approach that doesn't fully modernize the application or prevent dropped transactions during unexpected spikes. Amazon SNS is a publish/subscribe service, not ideal for buffering individual messages between services to prevent dropped transactions. It's designed for fan-out scenarios. While SQS can buffer messages between EC2 instances, this option still relies on managing EC2 instances, which is less operationally efficient than a fully serverless approach with Lambda. Monitoring SQS queue length to scale EC2 instances is a valid pattern, but not as efficient as serverless.