A company has a stateful web application that is hosted on Amazon EC2 instances in an Auto Scaling group. The instances run behind an Application Load Balancer (ALB) that has a single target group. The ALB is configured as the origin in an Amazon CloudFront distribution. Users are reporting random logouts from the web application.
Which combination of actions should a SysOps administrator take to resolve this problem? (Choose two.)
A. Change to the least outstanding requests algorithm on the ALB target group.
B. Configure cookie forwarding in the CloudFront distribution cache behavior.
C. Configure header forwarding in the CloudFront distribution cache behavior.
D. Enable group-level stickiness on the ALB listener rule.
E. Enable sticky sessions on the ALB target group.
Answers: B and E
This is related to logouts so you need a way to retain that login session – cookie can be forwarded in case of EC2 web use-case (not true for static web apps using S3 since S3 cannot process cookies).
More links:
https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/Cookies.html
You can configure each cache behaviour to do one of the following: Forward all cookies to your origin – CloudFront includes all cookies sent by the viewer when it forwards requests to the origin.
&
https://docs.aws.amazon.com/elasticloadbalancing/latest/application/sticky-sessions.html
By default, an Application Load Balancer routes each request independently to a registered target based on the chosen load-balancing algorithm.