IBM App Connect Enterprise software has provided the capability to connect to PostgreSQL from on-premises systems since version 10.0.0.6 by using the PostgreSQL LoopBack connector. In the latest release of IBM App Connect on IBM Cloud, the enterprise capability has been extended to allow the same PostgreSQL connectivity.
It is now possible to run integrations that connect to PostgreSQL either on premises or in the cloud without any need to modify the integration. PostgreSQL can be running in the cloud in a managed service like ElephantSQL, or on premises in your own managed system such as a Docker container. At any point, you can move the integration from cloud to on premises or vice versa with very little effort irrespective of where PostgreSQL is running.
The only step required in App Connect to allow the connectivity is to create a policy that defines the connection details:
The policy properties can be changed without any modification to the integration to enable access to PostgreSQL on premises or in a cloud managed service. It is also possible to provide a security identity that contains the user name and password to connect to PostgreSQL with.
For full details about how to configure both IBM App Connect (with a plan that provides enterprise capabilities) and PostgreSQL, see the tutorial Using IBM App Connect enterprise capabilities to invoke REST operations on a PostgreSQL database.