I agree with @Laetitia and will add that handle_call and the tuple it returns is your contract with GenServer. That logic belongs in the GenServer callback module. But you can certainly call out to shared logic in another module in the body of the function.
I’d also caution you about bottlenecking your system. You seem to want to make it easy to create multiple ets tables. Those are owned by a process for lifecycle management purposes and you’re not making them public (nor are you accepting a parameter to do so) so all access will have to go through a single GenServer, which only handles a single message at a time.
