AWS Certified Solutions Architect – Professional SAP-C01 – Question453

A company has an Amazon EC2 deployment that has the following architecture:

  • An application tier that contains 8 m4.xlarge instances
  • A Classic Load Balancer
  • Amazon S3 as a persistent data store

After one of the EC2 instances fails, users report very slow processing of their requests. A Solutions Architect must recommend design changes to maximize system reliability. The solution must minimize costs.
What should the Solutions Architect recommend?

A. Migrate the existing EC2 instances to a serverless deployment using AWS Lambda functions
B. Change the Classic Load Balancer to an Application Load Balancer
C. Replace the application tier with m4.large instances in an Auto Scaling group
D. Replace the application tier with 4 m4.2xlarge instances

Correct Answer: B

Explanation:

Explanation: By default, connection draining is enabled for Application Load Balancers but must be enabled for Classic Load Balancers. When Connection Draining is enabled and configured, the process of deregistering an instance from an Elastic Load Balancer gains an additional step. For the duration of the configured timeout, the load balancer will allow existing, in-flight requests made to an instance to complete, but it will not send any new requests to the instance. During this time, the API will report the status of the instance as InService, along with a message stating that “Instance deregistration currently in progress.” Once the timeout is reached, any remaining connections will be forcibly closed.
Reference:
https://docs.aws.amazon.com/autoscaling/ec2/userguide/attach-load-b…
https://aws.amazon.com/blogs/aws/elb-connection-draining-remove-ins…