AWS Certified Solutions Architect - Associate

Explanation

The correct answer is A because:

1. Current Architecture Issue: The application currently uses EC2 instances in a single Availability Zone, which creates a single point of failure. If that AZ goes down, the application becomes unavailable even though the RDS database is already Multi-AZ.

2. High Availability Requirements: To achieve high availability for the application tier, we need:

   • Multi-AZ deployment: EC2 instances should be distributed across multiple Availability Zones
   • Auto Scaling: Automatically replace failed instances
   • Load Balancer: Distribute traffic across healthy instances in multiple AZs

3. Why Option A is Correct:

   • Multi-AZ EC2 Auto Scaling: Ensures EC2 instances are launched across multiple Availability Zones
   • Application Load Balancer: Distributes incoming traffic across healthy instances in multiple AZs
   • This creates a highly available architecture where if one AZ fails, traffic is routed to instances in other AZs

4. Why Other Options are Incorrect:

   • Option B: Taking snapshots and sending them to another region is for disaster recovery, not high availability. It doesn't address the immediate availability issue.
   • Option C: Route 53 latency-based routing alone doesn't solve the single AZ problem. It routes traffic based on latency but doesn't provide instance redundancy across AZs.
   • Option D: While creating a Multi-AZ ALB is good, it doesn't address the EC2 instances being in a single AZ. Route 53 rules alone won't make the application highly available.

5. Complete Solution:

   • Deploy EC2 instances across multiple AZs using Auto Scaling groups
   • Use Application Load Balancer to distribute traffic
   • Configure health checks to route traffic only to healthy instances
   • The RDS Multi-AZ DB instance already provides database high availability

This approach ensures the application tier is highly available across multiple Availability Zones, meeting the company's requirements.