Issue related to index

Why it is showing this error?

I think this is happening because of the individual sizes of the followerId and followingId columns. So that when they're indexed together, the total size exceeds 767.

Can you tell if their type & size ?

this happens to me when i index an int i'm not sure how to fix this with a string but if i set the int limit to under 737 it works so it could possibly be a bug

In latest version, the string type is deprecated. There are other types available according to different sizes i.e. Text, Mediumtext, Longtext & Varchar. For attributes like ids, you can use Varchar as it has variable size