We plan to change the logic of the Amplitude user property "User ID" setup. Previously, we used to pass the value from our backend system there, and now we will start passing the firebase user id.
We are planning to rewrite the value of this user property to firebase.user_id for old users (i.e. for all those who will have the "User ID" value before the logic is changed).
Can our analytics "break" from changing the values for old users?
Hi
If you rewrite a new user ID for an existing user, Amplitude will recognize them as different unique users.
Also, user ids cannot be merged as mentioned in here - https://help.amplitude.com/hc/en-us/articles/115003135607#h_c323d7e5-4662-4a36-b0a1-5110a341e80c
I would recommend reading the backfill guide if you really have to update user ids on your events and ingest your historical data in a new Amplitude project.
Here’s a post for further reference -
Hope this helps.
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