Error Creating Load Balancer: InvalidConfigurationRequest

Thank you again Riku! This is related to the 403 Forbidden issue that I'm trying to resolve if you remember. If I configure the initial setup correctly this error will be resolved.

The subnetting configuration of my ALB is as follows: Availability Zones (AZs): I need to deploy the ALB across two Availability Zones (AZ1 and AZ2) to ensure high availability and fault tolerance. By distributing the ALB across multiple AZs, I can ensure that it can handle traffic even if one of the AZs experiences issues.

Subnets: In each of the selected Availability Zones, I will choose public subnets for the ALB placement. Public subnets are necessary to allow the ALB to receive incoming traffic from the internet and distribute it to backend instances running in private subnets.

Since I want my ALB to be accessible from the internet, I will configure it as an internet-facing load balancer. This will allow it to have a public IP address and handle incoming traffic from clients outside of my VPC. The ALB will be responsible for forwarding traffic to the backend instances running in private subnets. These backend instances will host my web application.

Can you please let me know what do you actually mean by "My assumption is that simply setting the public subnets of AZ1 and AZ2 to ALB will solve the problem"?

Thanks for replying. In other words, the error is caused by selecting a subnet in the same AZ. So you need to make sure that the subnet is selected correctly.

Thank you Riku and Gary for guiding me to the right direction. When I chose only 1 subnet for each zone, it was resolved. I selected a private subnet to each zone in EC2 and RDS and 1 public subnet to each zone in the load balancer.