Introduction
The purpose of this post is to compare, from the networking point of view, the hybrid cloud approach (application tier in Azure and the database tier in OCI), with the OCI native approach (both the Application and the Database tiers are in OCI).
Application tier in Azure and the Database tier in OCI
In this implementation, the application tier is in Azure and the Database tier will use the OCI Database services.
The connectivity between the Application and the Database leverages the Oracle Interconnect for Azure service.
With Interconnect, the customer can configure a private dedicated connection between Azure and OCI. This service uses the Fastconnect service on OCI and the ExpressRoute on Azure.
The customer pays for the Fastconnect and ExpressRoute services costs.
The Interconnect service is not available in all OCI regions, one of the reasons is the geographical distance between the OCI and Azure data centers (which would not deliver the expected 2ms latency) and another reason is the lack of customer demand in a specific region (the number of supported regions is growing constantly).
The reference architecture of the service can be found here.
Apllication and Database tiers native to OCI
When both of the tiers are provisioned in OCI the tiers are using the native OCI network and the latency is irrelevant.
There will be no cost associated with the connectivity.
The OCI Database Services are available in all the OCI regions and connectivity from the Application tier to the Database tier requires minimal configuration from the networking point of view.
Conclussion
The use of the Cloud Native approach will provide the best networking performance, minimal configuration, and no connectivity cost between the Application and the Database.