Recommended High Availablity Architecture
There's nothing particularly necessary for Craft here, other than what would be needed for a standard PHP application.

https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/php-ha-tutorial.html

And some potentially useful Craft related information around this topic here:

Load balancing nodes configuration (3 Craft nodes behind F5 Big-IP)

Craft admin login infinite redirect in cluster