For a highly available web application using a custom Amazon VPC with public and private subnets, how many subnets should you create?

When designing a highly available web application within a custom Amazon VPC featuring both public and private subnets, it’s essential to consider the architecture's redundancy and fault tolerance. Opting for a setup that provides high availability usually involves distributing the resources across multiple Availability Zones (AZs).

Typically, a highly available architecture would require at least one public and one private subnet in each Availability Zone. Since AWS recommends spreading resources across multiple AZs to ensure that your application remains functional in the event of an outage in one zone, the configuration usually includes:

1. Public Subnets: These allow direct access from the internet, where you can host load balancers, NAT gateways, or web servers that need to serve incoming traffic directly.

2. Private Subnets: These do not allow direct access from the internet, and they are commonly used for application servers or databases that should not be exposed directly to the outside world.

For a robust design, you would typically have:

• 1 public subnet in each Availability Zone.

• 1 private subnet in each Availability Zone.

This means that if you are operating in a region with at least two Availability Zones, you would need a minimum of 2 public subnets and 2 private subnets,