The string type is deprecated in the latest version. Use Text, Mediumtext, Longtext, and Varchar instead. Varchar is suitable for attributes like ids due to its variable size.
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.
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
