Level 2

Question

(CJA) How does persistence work with first/last known allocation & custom lookback windows?

Forum|Forum|22 days ago
March 16, 2026
2 replies
56 views

It is pretty straightforward when using first known or last known allocation with session expiration in Adobe CJA. It is less clear when a custom lookback window is used, because of both the forward and backward nature of these allocation types.

Example, if a user had the following sequence, what would be the first and last known values assuming the following

Day = the date in January
Chart date range is Jan 1 - Jan 31
Custom lookback window is 7 days for both the last known and first known properties.

Day	Value on Event	First Known	Last Known
1		C	C
5	C	C	B
9	B	C	B
14		B	A
18	A	B	A

Does custom lookback essentially work as custom look-forward for ‘last known’? Is the above correct?

MandyGeorge

Community Advisor and Adobe Champion

The look back window refers to where/when Adobe is looking for a value. If you’re using a person(visitor) container, then your lookback window is the number of days that you want to search for a value for that person.

For example, if my lookback window is 7 days and I do an action today, which is March 18th, it will look back to March 11th (7 days ago), and consider any values in that time period. Anything that happened March 10th or before won’t be considered.

But this still takes into account when the success events happened. So if I’m looking at cart additions, and my cart addition happened yesterday (March 17th), it would look back 7 days from when that happened..

So let’s look at your example. Someone visits on day 1, and no value in your variable of interest is passed. So any success events on day 1, won’t have a value at all.
Day 5 the value C is passed. Since that is the only value, both first touch and last touch attributions will have the same value.
Day 9, it’s less than 7 days since day 5, so the first touch will still persist, but the last touch will change to be B.
Day 14, no new value is set, but there is a success event, so it will look at the last 7 days. Day 5 was more than 7 days ago, so it’s now outside our lookback window. Meaning that the value from day 9 is the only value, so first and last touch will both be B.
Then we get to day 18. Day 9 was more than 7 days ago, and no value was set on day 14. So value A is going to be the first and last touch again.

Day	Value on Event	First Known	Last Known
1
5	C	C	C
9	B	C	B
14		B	B
18	A	A	A

P

PatrickJa6Author

Level 2

Thank you for taking the time to answer @MandyGeorge aka “winner of all rockstar competitions: :).

Let’s look at the table used by Adobe to explain first/last known.

‘Hit 1’ is able to receive a value from ‘hit 5’ when “last known” allocation is selected.
IMO, its really straightforward to interpret this with a session expiration. Exit page concept being a classic example.

I am trying to understand what happens when instead of session expiration the expiration is “custom time period”. Does the custom time period have any influence on how much into the future things are evaluated or does this basically just inherit a person scoped expiration within the date range?

Does that help clarify?

Jennifer_Dungan

Community Advisor and Adobe Champion

While I am not sure all the calculations that are done in CJA, I would expect the “last known” lookback won’t look into the future (ie. Jan 5, Jan 14).

You have the “Last Known” for events that haven’t happened as of those dates.

Example… On Jan 5th, you show the value being set to “C” and the first known as “C” which I agree with, but the last known as “B”… but looking back 7 days, there is no B… Lookback should only “look backwards” (it shouldn’t get values from the future… what would be the purpose of that? When trying to get attribution towards a conversion, why would you give credit to something the user hadn’t seen or interacted with yet?

It should look more like:

Day	Value on Event	First Known	Last Known
1		C	C
5	C	C	C
9	B	C	B
14		B	B
18	A	A	A

Note, that with a “7 Day lookback”, Jan 18th’s first known value should be “A” not “B”…. as “B” was set 9 days previously, and outside the lookback window.

P

PatrickJa6Author

Level 2

Thanks @Jennifer_Dungan ,
When I use a session as the expiration it does “look towards the future”.
Is the idea that if one selects ‘custom time’ instead of session expiration then only events prior to the given event are considered?

Jennifer_Dungan

Community Advisor and Adobe Champion

I don’t think it’s possible to look forward at all… the whole purpose of attribution is to understand what drove users to your site, or to convert… how could you ever count an action that hasn’t happened yet as a “driver” for your events??

Let’s look at am example:

Visit 1 - March 20

(Google Search)
Page A
- “Driver = search” (set when user enters the site)
Page B
- “Driver = search” (persisted value based on last touch)
Page C
- “Driver = search” (persisted value based on last touch)

Visit 2 - Mach 21

(Newsletter)
Page D
- “Driver = newsletter” (set when user enters the site)
Page E
- “Driver = newsletter” (persisted value based on last touch)
User Makes an Order
- “Driver = newsletter” (persisted value based on last touch)

Visit 3 - March 22

(Marketing Email)
Page F
- “Driver = marketing campaign” (set when user enters the site)
Page G
- “Driver = marketing campaign” (persisted value based on last touch)

Now, when you are building a report on March 23, and you are looking at your Orders

The Driver for the Order was “newsletter” based on the last touch. It was “search” if you look at first touch in 7 days. If you look at a participation model, you will see both search and newsletter.

But you should never see “marketing campaign” associated to that order… the user had not interacted with the marketing email before making their purchase…. to say that the marketing email helped to drive the purchase is a lie… the user has not seen that email, the email hasn’t even been sent when the order was made.

It shouldn’t matter if you choose a custom time, or session, or anything else… attribution can only look at what the user did before the conversion.

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