Questions 13 to 15

Explanations for questions 13 to 15

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Question 13

A company has launched a multi-tier application architecture. The web tier and database tier run on Amazon EC2 instances in private subnets within the same Availability Zone.

Which combination of steps should a solutions architect take to add high availability to this architecture? (Select TWO)

  1. Create new public subnets in the same AZ for high availability, and move the web tier to the public subnets.
  2. Create an Amazon EC2 Auto Scaling group and Application Load Balancer (ALB) spanning multiple AZs.
  3. Add the existing web application instances to an Auto Scaling group behind an Application Load Balancer (ALB).
  4. Create new private subnets in the same VPC but in a different AZ. Create a database using Amazon EC2 in one AZ.
  5. Create new private subnets in the same VPC but in a different AZ. Migrate the database to an Amazon RDS multi-AZ deployment.

Correct Answer: 2, 5

Explanation: The solutions architect can use an Auto Scaling group across multiple AZs with an ALB in front to create an elastic and highly available architecture. Then, they can migrate the database to an Amazon RDS Multi-AZ deployment to create HA for the database tier. This results in a fully redundant architecture that can withstand the failure of an Availability Zone.

INCORRECT:Create new public subnets in the same AZ for high availability, and move the web tier to the public subnets.” is incorrect. If subnets share the same AZ, they are not suitable for splitting your tier across them for HA as the failure of an AZ will take out both subnets.

CORRECT:Create an Amazon EC2 Auto Scaling group and Application Load Balancer (ALB) spanning multiple AZs.” is a correct answer.

INCORRECT:Add the existing web application instances to an Auto Scaling group behind an Application Load Balancer (ALB).” is incorrect. The instances are in a single AZ, so the solutions architect should create a new Auto Scaling group and launch instances across multiple AZs.

INCORRECT:Create new private subnets in the same VPC but in a different AZ. Create a database using Amazon EC2 in one AZ.” is incorrect. A database in a single AZ will not be highly available.

CORRECT:Create new private subnets in the same VPC but in a different AZ. Migrate the database to an Amazon RDS multi-AZ deployment.” is also a correct answer.

References: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-increase-availability.html

https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Concepts.MultiAZ.html

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