I recommend you have a good look at this topic, the associated video and in particular this post to get a better sense of the relevant use cases for distributed BEAM.
In short the general recommendation would be to not use distributed BEAM to communicate between MyPhoenixApp and MyBackendApp (given that they are running on separate nodes and consequently physically separate machines connected via an unspecified network).
Now that doesn’t mean that it can’t be used but one needs to be aware of a number of issues that this approach has which imposes some constraints on the technical infrastructure (e.g. the nodes are running in a secured environment on a common backplane or similar localized arrangement) that may or may not be a showstopper.
