In Legacy ID Management, the expected behavior is that when a user is anonymous, the distinct_id is set to the device ID (often a randomly generated value), and the user_id is null. When the user logs in or is identified, the distinct_id should typically switch to the user ID. However, if you observe that after the user is identified (i.e., user_id becomes not null), the distinct_id remains as the device ID, this suggests that the identification step did not update the distinct_id as expected.
The knowledge sources do not provide a detailed explanation for this specific scenario in Legacy ID Management. In the documented flows, after calling .identify(user_id), Mixpanel is expected to use the user ID as the distinct_id for subsequent events, not continue using the device ID Identifying Users (Original) - Example User Flows.
Possible reasons for this behavior, based on the documentation, could include:
- The .identify() method was not called correctly, or not called at all.
- There is a custom implementation or event ingestion method that continues to set the distinct_id to the device ID even after identification.
- The SDK or integration being used does not follow the standard Legacy ID Management flow.
However, the knowledge sources do not explicitly describe a scenario in Legacy ID Management where user_id becomes not null but distinct_id remains as the device ID. Therefore, I'm sorry, but there's no information in the knowledge sources that fully explains why this happens in Legacy ID Management.
