Your company has a new web application that needs to be deployed in AWS as soon as possible. The application is backed in an AMI, and you plan to use an Application Load Balancer to distribute the traffic to an Auto Scaling group. Which of the following methods helps you to achieve a highly available system?

Answer options:

A.Assign an Elastic IP to each instance under the Auto Scaling group.
B.Use the Application Load Balancer to send traffic across instances in multiple availability zones.
C.Configure the Application Load Balancer to distribute traffic to instances in multiple AWS regions.
D.Assign a dedicated IP address to the Application Load Balancer.

Correct Answer – B
Refer to https://d1.awsstatic.com/whitepapers/aws-building-fault-tolerant-applications.pdf for how to build highly available and fault-tolerant software systems in AWS.
Option A is incorrect: It is not necessary to assign Elastic IPs to ASG instances. The instances may be terminated when the ASG scales in and new instances will be created.
Option B is CORRECT: Because this ensures that when one availability zone has an outage, instances in other availability zones can still serve traffic from the Application Load Balancer.
Option C is incorrect: Because Application Load Balancer is a regional service and cannot distribute traffic to instances in multiple regions.
Option D is incorrect: Because users cannot assign IP addresses to an Application Load Balancer.