Architectures

Question 1

What does a stateless web app consist of?

Answer 1

-a route 53 dns configuration that points to a load balancer. The load balancer has health checks and spreads over multiple azs. The underlying ec2 instances are organized in an autoscaling group across multiple azs and have reserved instances to reduce cost.

Question 2

What does a stateful web app consist of?

Answer 2

• a route 53 dns configuration that points to a load balancer. The load balancer has health checks and spreads over multiple azs. It implements sticky sessions for dealing with user sessions. The underlying ec2 instances are organized in an autoscaling group across multiple azs and have reserved instances to reduce cost.
• Elasticache is introduced to store user sessions. User data is stored in e.g. amazon rds. rds can be read replicated. Cache can be organized in a write through manner.

For security purposes the security groups of the ec2 instances only let traffic from the load balancer in. Access to the rds and elasticache are restricted only to the ec2 security group.

For redundancy all services are multi az.

In case files need to be stored and accessed throughout ec2 instances you should connect efs through eni cards.