I group functions with the same name in a Module

defmodule MyMod do
  
  def foo(1)
  def foo({1, 2})

  def bar()

end

But in a GenServer this can get messy when you have several public interfaces as you get a lot of handle_call or handle_cast definitions dealing with the different public interfaces.

What do you do in this case?
You keep all the callbacks grouped together:

defmodule MyMod do
  use GenServer
  ...
  def handle_cast(:foo, _from, %{})
  def handle_cast(:foo, _from, state)
  def handle_cast(:bar, _from, %{})
  def handle_cast(:bar, _from, state)
  ...
end

or group them by case:

defmodule MyMod do
  use GenServer
  ...
  def handle_cast(:foo, _from, %{})
  def handle_cast(:foo, _from, state)
  
  def handle_cast(:bar, _from, %{})
  def handle_cast(:bar, _from, state)
  ...
end

I prefer the latter when the public API is broad