@Niharika I've added a section to explain the differences from the user's perspective

Change 777786 had a related patch set uploaded (by STran; author: STran):

[mediawiki/extensions/IPInfo@master] Use localStorage instead of user options for infobox state

https://gerrit.wikimedia.org/r/777786

Testing this is still affected by T305650, so it might be better to test it after that one

Change 777786 merged by jenkins-bot:

[mediawiki/extensions/IPInfo@master] Use localStorage instead of user options for infobox state

https://gerrit.wikimedia.org/r/777786

Did regression on the expand and collapse of the IP info box on supported browsers(IE, Chrome, FF, Safari, Opera, Edge)
the user preference is sustained most times.

I lightly suspect the clean up might not be working as intended. Without the server being aware of a default value, I think setting 0 is either doing nothing, or actively inserting new rows for everyone. I'm not sure how it would be resulting in removing existing rows for users that stored a non-default/non-zero value in the past. Might be worth double checking that this has the desired effect on the database table.

If I understand correctly, the change did not account for transitioning it. That seems fine (it's a small effort to open it again), but that also means the existing data could presumably be removed in one go from the server-side without deferring this to the client. This is something one would need for localStorage, but not for user.options. E.g. we could run a single DELETE query for this in beta and (if in prod) in prod as well. Alternatively, one could wait for T300371 to take care of it as that task is likely to result in any change to user options to naturally delete any rows for invalid/unknown keys.

Without the server being aware of a default value, I think setting 0 is either doing nothing, or actively inserting new rows for everyone.

Ah yes, we shouldn't have removed the default in the patch (setting the default value would remove the row). As it is, it is throwing the warning but shouldn't be inserting new rows.

We added this into the app rather than just running a query in production, since in theory the extension could be being used by third parties (however, it's probably unlikely, given how new it is, plus the need for a maxmind subscription).

We could add the default value back until T305838: Remove line to clean up old user preference, or just do T305838 now, given the unlikeliness of this being used outside Wikimedia, plus the existence of T300371: Drop now unused user preferences from production database(s).