SAA-C03 Question 91
Select 2A company is migrating its web application to AWS and wants to ensure high availability and fault tolerance for its application. The application is deployed on Amazon EC2 instances fronted by an Application Load Balancer. The company’s primary goal is to ensure that the application remains available even if an entire Availability Zone goes down. Which of the following architecture choices will meet this requirement?
- A
Deploy EC2 instances in multiple Availability Zones and attach them to the Application Load Balancer.
- B
Enable Auto Scaling for the EC2 instances and configure it to span across multiple Availability Zones.
- C
Deploy EC2 instances in a single Availability Zone and set up an Application Load Balancer in front of them.
- D
Use Elastic Load Balancing's cross-zone load balancing feature to distribute traffic across instances in different regions.
- E
Deploy the Application Load Balancer and EC2 instances in different Availability Zones to ensure fault tolerance.
Show answer and explanation
Correct answers: A, B
Explanation
To achieve high availability and fault tolerance, EC2 instances must be deployed in multiple Availability Zones, and Auto Scaling should be configured to span these zones. This ensures that the application remains operational even if an entire Availability Zone experiences a failure. The Application Load Balancer will route traffic to healthy instances in other zones as needed.
- A. Correct.
Correct: Deploying EC2 instances in multiple Availability Zones ensures that the application can handle the failure of an entire Availability Zone, as traffic will be routed to healthy instances in other zones.
- B. Correct.
Correct: Enabling Auto Scaling across multiple Availability Zones ensures that new instances can be launched in healthy zones in case of increased demand or failure in one zone.
- C. Incorrect.
Incorrect: Deploying EC2 instances in a single Availability Zone creates a single point of failure. If the Availability Zone goes down, the application will become unavailable.
- D. Incorrect.
Incorrect: Elastic Load Balancing's cross-zone load balancing feature distributes traffic evenly across instances in different zones within the same region, but it does not enable high availability if EC2 instances are only in a single Availability Zone.
- E. Incorrect.
Incorrect: Deploying the Application Load Balancer and EC2 instances in different Availability Zones does not meet the requirement. Both the load balancer and instances need to span multiple Availability Zones to achieve fault tolerance.