This guide walks through an example journey for sending appointment reminders to users. This guide highlights the use of Event Entry Journeys, Keyed Performed Segments, and Keyed Performed User Properties. This journey will perform the following steps:
  1. Wait until 1 day before the appointment time.
  2. Check if the user has cancelled their appointment.
  3. If the appointment has not been cancelled, send an appointment reminder.
  4. Wait for the user to confirm that they have attended the appointment.
  5. Send a thank you message to the user.

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Creating the Journey

First, we’ll create a new event entry journey, listening for the APPOINTMENT_BOOKED event, keyed on the appointmentId property. 
{
  "event": "APPOINTMENT_BOOKED",
  "type": "track",
  "properties": {
    "appointmentId": "123",
    "className": "Yoga",
    "appointmentTime": "2024-12-01T10:00:00Z"
  },
  ...
}
Appointment Reminders Entry
Then, we’ll create a new user property, on that same APPOINTMENT_BOOKED event, with the same appointmentId key, but rendering the appointment time as the value.
Appointment Reminders Time User Property
Then we’ll create a delay node, using the user property variant, with the user property being the appointmentTime user property we just created. We’ll set an offset of 1 day prior to the appointment time.
Appointment Reminders Delay
Note, that because both the event entry node and the user property node have the same appointmentId key, we can be sure that the user property will wait on the same appointmentTime specified in the trigger event, as opposed to any other concurrent APPOINTMENT_BOOKED events. Next, we’ll create a segment which looks for APPOINTMENT_CANCELLED events, keyed on the appointmentId property. 
{
  "event": "APPOINTMENT_CANCELLED",
  "properties": {
    "appointmentId": "123"
  },
  ...
}
Similarly, because the appointmentCancelled segment and our journey are both keyed on the appointmentId property, the segment will wait on a cancellation event that corresponds to the same appointment booking used to trigger the journey.
Appointment Reminders Cancelled
Then we’ll use this segment to create a segment split, to check if the appointment has been cancelled.
Appointment Reminders Cancelled Split
Next, we’ll create a user property for rendering the class name in the message.
Appointment Reminders Class Name User Property
Then, we’ll create a message node to send an appointment reminder, with the message template using the class name user property.
Appointment Reminders Message
We’ll now need to create a segment to check if the user has confirmed that they have attended the appointment. 
{
  "event": "APPOINTMENT_CONFIRMED",
  "properties": {
    "appointmentId": "123"
  },
  ...
}
Appointment Reminders Confirmed
Then we’ll incorporate this segment into a wait-for node, to wait for the user to confirm that they have attended the appointment.
Appointment Reminders Confirmed Wait For
Finally, we’ll create a message node to send a thank you message to the user.
Appointment Reminders Thank You