This image shows a 3-tier topology consisting of a load balancer (LB), an autoscaling web tier, and an Oracle Autonomous Transaction Processing database. All the resources are deployed in a single availability domain in an Oracle Cloud Infrastructure region. The LB tier, web tier, and database tier are isolated in separate subnets within a single VCN. Network security groups (NSGs) regulate the network traffic to and from the resources in each tier. A route table attached to each subnet contains rules to direct traffic destined for targets outside the VCN.

• Client requests flow in through an internet gateway to the public LB, which distributes the requests to the web tier.
• The web tier consists of an autoscaling pool of compute instances defined by using an instance configuration. The compute instances are distributed evenly across all the fault domains in the availability domain. All the compute instances in the web tier are attached to a private subnet.
• The database tier consists of Oracle Autonomous Transaction Processing database attached to a private subnet.