This image shows how you can deploy Oracle REST Data Service with high availability on Oracle Cloud Infrastructure. It shows two OCI regions labeled Oracle Cloud Region containing a single a Virtual Cloud Network (VCN), which itself contains two availability domains (Availability Domain 1 and Availability Domain N.

Availability Domain 1 contains two fault domains (Fault Domain 1 and Fault Domain 2). The VCN also contains these three regional subnets, one public and two private, which span both fault domains:

Public Regional Subnet A, which contains an API Gateway external to the fault domains and, within the fault domains the load balancer tier. Each fault domain contains a load balancer; fault domain 1 is an active load balancer while fault domain 2 has the standby load balancer. Access to the subneet is restricted by a security list and to the load balancer tier by a network security group (NSG).
Public Regional Subnet B, which contains the Oracle REST Data Services (ORDS) tier and extends outside the availability domain, although still within the VCN. The image shows one ORDS instance in each fault domain. Access to the subnet is restricted by a security list; an NSG in both fault domains controls access to both of those components.
Public Regional Subnet C, which contains the Database tier. It contains a single active database, exclusively within fault domain 1. Access to the subnet is restricted by a security list; an NSG restricts accesss to the fault domain.

Availability Doman N a single instance of ORDS, labeled ORDS Instance N.

Outside of the VCN but within the regionis an object storage for database backups instance.

OCI Region 2 contains Private Regional Subnet N, which comprises a standby database tier. Access to the subnet is restricted by a security list; an NSG restricts accesss to the fault domain.

The end user accesses Public Regional Subnet A bidirectionally through an Internet Gateway and on to the load balancer in Fault Domain 1. The standby load balancer in Fault Domain 2 can be accessed if necessary. The load balancer distributes traffic to the ORDS instances in Private Regional Subnet B (the ORDS tier). Instances in both fault domains communicate bidirectionally with the database in Private Regional Subnet C.

The database backs up data to object storage, which is within the region but outside the availability domain and the VCN. It also communicates bidirectionally, via DataGuard Sync, with a database in the load balancer tier within a private regional subnet in OCI Region 2.