I have a simple system made of a database backend, several instances of a web application and a load balancer. Each service is running in its own Docker container, all of them being hosted on the same physical server. The load balancer listens on the port 80 which is mapped to the same port on the host. All ingress/egress traffic is supposed to pass through that load balancer.
Currently, all those containers are attached to a single user-defined bridge.
I read it would be better to connect the load balancer and the app instances through one bridge, and the app instances and the database through a second one. Instinctively, it makes sense to avoid putting the DB on the public-facing bridge. But objectively, in a dockerized environment, what are the benefits of using two bridge networks instead of only one here? Which kind of threats is mitigated by doing so?