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Request for Assistance: Backfilling Missing Event Property in Mixpanel

Avatar of Yong S.Yong S.
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Hey dear team! We are missing a custom property on an event between 11/07/2025 to 11/12/2025 . And we are exploring ways to backfill the property to historical 94K events. What we tried:

  • export the event, backfill the property, and import to mixpanel with same $insertId, ends up with duplicate events

  • borrowed property: difficult on our data warehouse to combine the borrowed properties

Do we have a recommended way to backfill the missing property? Thanks!

1 comment

  • Avatar of linyee
    linyee
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    As outlined in the engineering blog, events can be deduplicated if they share the same:

    • Event name

    • distinct_id

    • Time value

    • $insert_id

    When all four keys match, the events are treated as duplicates, and only one is shown. I understand you now have duplicate events. A workaround is to filter by the backfilled property(is set) when querying the data.

    :mixpanel-new:1