sorted by created_at in this case is very misleading because it's the date of the last follow but we cannot know for sure who that follow was without a more complete history of that specific list, so unless your key is the last in the tags array (supposing it was appended) the created_at date is kind of meaningless, i.e if someone follows you since a year ago but just updated it's follow list to include someone else now, it would show up as the most recent follow list that you're in, but not the last one to add you..