Problem statement
Authorization Extension is limited and the users can’t login.
Cause
No workaround is possible since the 500kb limitation can’t be overridden. The Authorization Extension is not deprecated, but it won’t be expanded.
Solution
The general idea for a workaround that we can suggest would be to get under the limit and try to switch to Core as fast as possible. So, as a countermeasure, we can recommend that you clean up your database of inactive users. Maybe a trade-off could be that some users have to deal with the lack of permissions for a bit, but letting others sign-in normally. This is based on the idea that the easiest thing to do would be to get under the limit, but how much data you would need to remove is unknown. Generally, limits are cloud hard limits, so they abruptly end with no warnings.
Furthermore, you could use bulk upload jobs to bulk update the users into the right roles, in a route to get switched over to Authorization Core. Maybe you don’t have to do it for everyone and target a specific role that would be migrated from the Extension to Core, and then be removed from the Extension. That will free up some space as well.