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AWS Certified Solutions Architect - Associate Exam Question Walkthrough
Understand a key question on high availability for the AWS SAA-C03 exam. Learn how to identify the best solution for multi-tier applications.
Designing a multi-tier web application on AWS can be tricky, especially when it comes to ensuring high availability. Many candidates get tripped up on questions about automatic failover and traffic rerouting. This question tests your understanding of how to configure AWS services to maintain application availability during server failures.
The question
You are designing a multi-tier web application that will run on AWS. The application requires that if one of the application servers fails, traffic should be rerouted to another healthy instance automatically. Which configuration would best achieve this?
- A. Use an Auto Scaling group with an Application Load Balancer.
- B. Set up Amazon EC2 instances with individual Elastic IP addresses.
- C. Create a CloudFormation stack to deploy instances.
- D. Implement Route 53 with health checks.
Think before you scroll
Before you look at the answer, consider the goal: automatic rerouting of traffic if an application server fails. Think about which AWS services can monitor instance health and manage traffic distribution effectively.
The answer
The correct option is A. Use an Auto Scaling group with an Application Load Balancer. This configuration allows for automatic failover and load balancing, ensuring that traffic is routed to healthy instances when one fails. It provides high availability by managing both instance health and traffic distribution.
Why the other options lose
B. Set up Amazon EC2 instances with individual Elastic IP addresses. This option does not offer automatic failover or load balancing. If an instance fails, traffic will not be redirected unless manually configured, which defeats the purpose of high availability.
C. Create a CloudFormation stack to deploy instances. While CloudFormation helps in provisioning resources, it does not handle traffic management or automatic failover. Once instances are deployed, additional configurations are needed to ensure availability.
D. Implement Route 53 with health checks. Route 53 can route traffic based on health checks but is not a complete solution for application load balancing. It works best in conjunction with an Application Load Balancer or other traffic management solutions to reroute traffic effectively.
The concept behind it
The key principle here is high availability through automated traffic management. An Auto Scaling group combined with an Application Load Balancer not only distributes incoming traffic but also monitors the health of instances. If an instance fails, the Load Balancer automatically redirects traffic to healthy instances, ensuring uninterrupted service.
Exam trap to remember
Always consider both traffic management and health monitoring when designing for high availability. The two-question rule: if an instance fails, how does traffic get handled? Choose configurations that address both aspects directly.