A company migrated a message-processing system to AWS. Messages are received in an ActiveMQ queue on an Amazon EC2 instance, processed by a consumer application on Amazon EC2, and results are written to a MySQL database on Amazon EC2. The company wants the application to be highly available with low operational complexity. Which architecture offers the HIGHEST availability?

The correct option provides the highest availability and lowest operational complexity by leveraging managed AWS services. Amazon MQ with active/standby brokers across two Availability Zones ensures high availability for the message queue without requiring manual setup or management. An Auto Scaling group for consumer EC2 instances automatically scales and distributes instances across multiple AZs, handling failures and traffic spikes. Amazon RDS for MySQL with Multi-AZ enabled provides automatic failover and data replication for the database. Option 1 is incorrect because it uses self-managed ActiveMQ and MySQL on EC2, which increases operational complexity and requires manual replication and failover mechanisms. Option 2 is better than Option 1 by using Amazon MQ, but still uses a self-managed MySQL database on EC2, which lacks the high availability features of RDS Multi-AZ. Option 3 is better than Option 2 by using RDS Multi-AZ, but still relies on manually adding an additional consumer EC2 instance, which doesn't offer the automatic scaling and resilience of an Auto Scaling group.