Without going into stuff like Kubernetes, basically what you want is to run your postgres instances behind a load-balancer listening to 5432 and forwarding to w

Without going into stuff like Kubernetes, basically what you want is to run your postgres instances behind a load-balancer listening to 5432 and forwarding to whatever instance. The most common with postgres is probably HAProxy. If your problem is that you want to run unrelated instance of postgres... you don't really have a problem to begin with. Either use docker run to run your postgres image on different ports with different volumes, or just make a docker-compose YAML file with a bunch of postgres services. It's not like you have to have a single one.