When you update the conditions in an existing cohort that's being synced via webhook with a recurring sync, Mixpanel will send the differences (diffs) between the previous cohort state and the new cohort state. This means you'll receive:
- add_members actions for users who newly qualify for the cohort based on your updated conditions
- remove_members actions for users who no longer qualify for the cohort based on your updated conditions
Mixpanel stores a snapshot of the cohort state from the last successful sync and uses this to compute the differences. These diffs are then sent to your webhook via the add_members and remove_members calls during the next scheduled sync (which occurs every 30 minutes).
You would only receive a full members action in specific cases:
1. When the cohort is synced for the first time
2. If your webhook server was down (returning 429 or 5XX errors) for more than 3 days, causing the snapshot to expire
As explained in the documentation:
"Subsequent syncs include only differences in membership since the previous successful sync in order to preserve bandwidth, through a diffing mechanism."
Mixpanel Webhook Sync Documentation
