# How Send Time Optimization works

When an audience arrives at the Send time optimization stage in the STO Program, it will look up each audience member’s RIID_ against the selected Send Time Optimization PET to retrieve the earliest optimal send time from the moment of arrival (to the stage) through the next 24 hours. We refer to this 24 hour timeframe as the “send period”.

## Send Time Optimization example

To better explain how it works, let’s assume an audience arrives at the Send time optimization stage on Monday, 9am. This means the send period is Monday, 9am through Tuesday, 8am. The Send time optimization stage references the assigned Send Time Optimization PET and retrieves the optimal send times for each audience member for Monday and Tuesday, the days within the send period. Here is an example of the Send Time Optimization PET and the data retrieved:

RIID_

MONDAY

TUESDAY

6431679764

12

7

7974317975

6

5

3284084084

7

6854635377

0

23

2564367589

From there, the Send time optimization stage looks for the earliest optimal send time within the send period, which is from Monday, 9am through Tuesday, 8am. Using the same Send Time Optimization PET example, here is a chart showing the optimal send time that has been determined for each audience member in bold and the reason why it was selected.

RIID_

MONDAY

TUESDAY

REASON

6431679764

12

7

Monday at 12pm is the earliest optimal send time during the send period.

7974317975

6

5

Tuesday at 5am is the earliest optimal send time because Monday at 6am has past and is outside of the send period.

3284084084

7

Tuesday at 7am is the earliest and only optimal send time during the send period.

6854635377

0

23

The optimal send times for both days are outside of the send period so this audience member will be considered one without STO data.

2564367589

There are no optimal send times for either days during the send period so this audience member will be considered one without STO data.

The Send time optimization stage has determined audience members with RIID_s 6431679764, 7974317975, and 3284084084 have optimal send times within the send period and the stage will move them to the next stage along the “With STO Data” path at the optimal send time. For audience members with RIID_s 6854635377 and 2564367589, they have no optimal send times within the send period and the stage will move them to the next stage along the “Without STO Data” path.