At this point, the wizard asks us to provide some details for the Auto Scaling part at the beginning of the configuration process. It is okay to start with 1 instance to first check whether or not everything is working well.

VPC and subnets that you specify in the Auto Scaling group can be the same used in the previous example. But keep in mind, for the ALB it is mandatory to choose a public subnet while for the EC2 you can use a private or a public subnet. In Chapter 5, Adding Continuous Integration and Continuous Deployment we focus on security, we will explain why it is beneficial to insert the EC2 in private ones.

However, for now, it is okay to use any subnet. The important thing to do is to choose more than one subnets in different AZs:

For the security group, choose the one assigned to the EC2 machine in precedence; don't create a new one:

Use a key-pair that you own for a normal EC2. In theory, you don't need to log in to a machine managed by Auto Scaling. You only need a key to log in if there are errors and it is necessary to debug something: