The paragraph on page 30 is printed twice.

You also shouldn’t use notifiers to trigger further internal processing. For
example, if someone signs up for notifications for a certain flight, that may
trigger the creation of a flight monitor Elixir process or a message broker
subscription. This isn’t the job of a notifier, but instead is the responsibility
of a process manager, which you’ll explore in Chapter 4, “Exploring the Saga
of the Process Manager,” on page 47.