You are currently planning to use Autoscaling to launch instances that have an application installed. Which of the following methods will help ensure the instances are up and running in the shortest span of time to take in traffic from the users?

Answer options:

A.Log into each instance and install the software.
B.Use UserData to launch scripts to install the software.
C.Use Docker containers to launch the software.
D.Use AMI`s which already have the software installed.

Answer - D
The AMI will be the fastest because it will already have the software installed. You can customize the instance that you launch from a public AMI and then save that configuration as a custom AMI for your own use. Instances that you launch from your AMI use all the customizations that you`ve made.
For more information on AMI’s, please refer to the below link
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/AMIs.html