A company wants to design a reliable web application that is hosted on Amazon EC2.

The approach that will achieve the goal of designing a reliable web application that is hosted on Amazon EC2 is to spread EC2 instances across more than one Availability Zone. An Availability Zone is a physically isolated location within an AWS Region that has its own power, cooling, and network connectivity. By spreading EC2 instances across multiple Availability Zones, users can increase the fault tolerance and availability of their web applications, as well as reduce latency for end users2. Launching large EC2 instances in the same Availability Zone, spreading EC2 instances across more than one security group, or using an Amazon Machine Image (AMI) from AWS Marketplace are not sufficient to ensure reliability, as they do not provide redundancy or resilience in case of an outage in one Availability Zone.