A developer has a stateful web server on-premises that is being migrated to AWS. The developer must have greater elasticity in the new design. How should the developer re-factor the application to make it more elastic? (Choose two.)
A.
Use pessimistic concurrency on Amazon DynamoDB.
B.
Use Amazon CloudFront with an Auto Scaling group.
C.
Use Amazon CloudFront with an AWS Web Application Firewall.
D.
Store session state data in an Amazon DynamoDB table.
A - Not really relevant
B - Stateful suggests non static requests, so does this really help?
C - WAF is for security not elasticity
D - As the app is stateful the sessions need to go somewhere, so this makes sense.
E - Allows the app running on EC2 to scale, this is your elasticity.
elasticity
1. the ability of an object or material to resume its normal shape after being stretched or compressed; stretchiness.
2.ability to change and adapt; adaptability.
I will vote D and E.
In order to store user session data we can use DynamoDB (D is correct). To guarantee elasticity ELB+AutoScaling Group is the best option (also E is correct).
DE
The most elastic and scalable solution for storing session state data in a web application is to use an Amazon DynamoDB table. This is because DynamoDB is a highly scalable and managed NoSQL database that can handle large amounts of read and write requests, making it well-suited for storing session state data.
Using an ELB with an Auto Scaling group is another way to make the application more elastic. An ELB (Elastic Load Balancer) is a managed load balancing service that can automatically distribute incoming application traffic across multiple Amazon EC2 instances in an Auto Scaling group, improving the application's availability and scalability.
Should we not use ELB as an origin for Cloudfront?
Cache management can be done nicely, also Cloudfront can serve dynamic content, not sure why we are not considering it.
As for me B, E is the answer. D is correct, but the B, E can also handle this, as better pair up
Also found this in docs ,
"Some advantages with utilizing sticky sessions are that it’s cost effective due to the fact you are storing sessions on the same web servers running your applications and that retrieval of those sessions is generally fast because it eliminates network latency. A drawback for using storing sessions on an individual node is that in the event of a failure, you are likely to lose the sessions that were resident on the failed node. In addition, in the event the number of your web servers change, for example a scale-up scenario, it’s possible that the traffic may be unequally spread across the web servers as active sessions may exist on particular servers. If not mitigated properly, this can hinder the scalability of your application"
It is B an D.
B) https://linuxacademy.com/community/show/6241-why-use-autoscaling-and-cdn-cloudfront-at-the-same-time/
D) https://acloud.guru/forums/aws-certified-solutions-architect-associate/discussion/-KGu3LN1mb6yGbg5Dh26/stateless-application-services
You can do all that but that it's not mentioned about what's behind the alb and the best solution is one which is more flexible here, dynamodb is made for scaling
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