User's google calendar ID changes when primary email is updated

Question

Essentially I've noticed that when a user's primary email is updated on their google account, their calendar ID will also change (e.g. ID will change from [email protected] to [email protected]).

This is a problem because I work on an application that relies on the calendar ID being a stable identifier for users. For example, lets say user A at a company schedules an event to their calendar through my application. We'll save metadata related to that event in our own database along with user A's calendar ID to denote that the event was scheduled to that calendar. This is important because we use this information to ensure that only users with write access to this calendar ID can edit this event from our application (important for security purposes).

Lets say user A gets their primary email updated, which causes their calendar ID to also change. Now, when I query the CalendarList endpoint to get a list of user A's calendars, I get back the new calendar ID, which makes my application think that user A should not have access to edit the event they just scheduled since that event was scheduled to a calendar ID that user A no longer has access to.

Is there a way around a problem like this? I can't find an endpoint that will return user A's "archived" calendar ID in addition to their new one. More deeply, I don't understand why their calendar ID changes as it feels like IDs should be stable identifiers...

Answer 1

In this case, by testing and working with the calendar API and Google Workspace it's a fact that the Calendar ID will always be the email address of the user account it’s associated with. I wish there was actual documentation but this is only from testing that I have verified this. There are other threads that explain the same, in this case with your situation you should modify your app in a way that the CalendarID is not based in a stable ID, as this depends on your email address.