Hi,

Take a look at the Building Umbrella Project from elxirconf: https://github.com/poteto/elixirconf-201620 by Wojtek Mach.

The source: https://github.com/wojtekmach/acme_bank22 is a great example of an umbrella app. For example, he uses two instances of phoenix (backoffice and bank_web). It's a working app, so you can experiment with it too.

The talk is here: https://www.youtube.com/watch?v=6NTmUQClHrU18 I found it very instructive.