AWS — Three-Tier Web Application, Multi-AZ

The reference architecture, drawn correctly and reported clean: a public load balancer, application servers in private subnets across two availability zones, and the database isolated with a standby in the other zone. Copy this one. Every check runs and finds nothing, which the engine states rather than implies.

Cloud architectureArchitecture Cloud architecture syntax docs

Template previewCloud architecture

Make it your own.

title "Three-tier web application"
provider aws

internet {
  user customers "Customers"
}

cloud prod "Acme Production" {
  region us-east-1 {
    network vpc-main "Main VPC" cidr 10.0.0.0/16 {
      alb lb "Public load balancer"
      igw gw "Internet gateway"
      s3 assets "Static assets"

      zone us-east-1a {
        subnet pub-a "Public A" public cidr 10.0.1.0/24 {
          nat nat-a "NAT gateway A"
        }
        subnet app-a "App tier A" private cidr 10.0.11.0/24 {
          ec2 web-a "Web server A" count 2 tier web
        }
        subnet data-a "Data A" isolated cidr 10.0.21.0/24 {
          rds db-a "Orders (primary)" multi-az
        }
      }

      zone us-east-1b {
        subnet pub-b "Public B" public cidr 10.0.2.0/24 {
          nat nat-b "NAT gateway B"
        }
        subnet app-b "App tier B" private cidr 10.0.12.0/24 {
          ec2 web-b "Web server B" count 2 tier web
        }
        subnet data-b "Data B" isolated cidr 10.0.22.0/24 {
          rds db-b "Orders (standby)" multi-az
        }
      }
    }
  }
}

customers -> lb : https 443
lb -> web-a : http 8080
lb -> web-b : http 8080
web-a -> db-a : postgres 5432
web-b -> db-a : postgres 5432
db-a <=> db-b : replication
web-a => assets : s3 api
web-b => assets : s3 api
lb ..> gw
web-a ..> nat-a
web-b ..> nat-b