A company runs an application in (he cloud that consists of a database and a website Users can post data to the website, have the data processed, and…

The application's reliability issues stem from single points of failure in both the web and database tiers. To address the website outages, the single EC2 instance must be replaced with a scalable and fault-tolerant architecture. Placing the Tomcat servers into an Auto Scaling group behind an Application Load Balancer (A) allows the application to handle traffic spikes and recover from instance failures. For this architecture to be highly available, it must operate across multiple Availability Zones (AZs), necessitating the creation of an additional public subnet in a different AZ (F). Furthermore, the single MySQL database instance is a critical single point of failure. Migrating to Amazon Aurora with a replica (C) introduces a managed, fault-tolerant database with automatic failover, significantly enhancing data tier reliability.

B. A single VPC peering connection is managed by AWS and is not a single point of failure; adding another is unnecessary and not possible between the same two VPCs.
D. NAT gateways are for outbound internet access from private subnets and do not help resolve outages caused by high inbound traffic to the website.
E. Moving the Tomcat server to the database VPC does not resolve the core issue of it being a single, non-scalable instance that fails under load.

1. Auto Scaling and Load Balancing (A

F): The AWS documentation states that to achieve high availability

you should distribute traffic across instances in multiple Availability Zones. An Application Load Balancer requires at least two AZs to be configured for fault tolerance. An Auto Scaling group works with the load balancer to automatically adjust capacity.

Source: AWS Documentation

"Tutorial: Set up a scaled and load-balanced application"

Step 2: Choose a VPC and subnets. The tutorial specifies selecting at least two public subnets in different Availability Zones.

2. Amazon Aurora for High Availability (C): Amazon Aurora is designed for high availability. An Aurora DB cluster consists of a primary DB instance and one or more Aurora Replicas. If the primary instance fails

Aurora automatically fails over to a replica.

Source: AWS Documentation

"High availability for Amazon Aurora"

Section: "Amazon Aurora high availability".

3. VPC Peering Redundancy (B): The infrastructure for a VPC peering connection is created to be neither a single point of failure nor a bandwidth bottleneck.

Source: AWS Documentation

"VPC Peering Guide"

Section: "VPC peering basics"

under "What is VPC peering?".