A company runs a business-critical web application on Amazon EC2 instances behind an Application Load Balancer in an Auto Scaling group. The application uses an Amazon Aurora PostgreSQL database deployed in a single Availability Zone. The company wants high availability with minimal downtime and minimal data loss, and with the least operational effort. Which solution meets these requirements?

The correct solution ensures high availability and minimal downtime/data loss with low operational effort. Configuring the Auto Scaling group across multiple Availability Zones (AZs) distributes EC2 instances, so if one AZ fails, the application remains available. A Multi-AZ Aurora PostgreSQL database automatically provisions a standby replica in a different AZ, providing automatic failover with minimal data loss (RPO of seconds) and downtime (RTO of minutes) in case of a primary database failure. Amazon RDS Proxy further enhances availability by managing connection pooling and automatically routing connections to the new primary instance during failover, reducing application disruption. Placing EC2 instances in different AWS Regions and using Cross-Region Replication for Aurora adds significant latency and complexity, and is typically for disaster recovery, not high availability within a region. Configuring the Auto Scaling group in one AZ creates a single point of failure for the application tier, and hourly database snapshots lead to significant data loss (up to an hour) and recovery time. Using multiple AWS Regions for the Auto Scaling group and writing data to S3 with Lambda for database updates is overly complex and introduces eventual consistency challenges, which is unsuitable for a business-critical application requiring minimal data loss.