SELECT 
  `staff_id`, 
  `name`, 
  `last_name`, 
  `function`, 
  `user_id`, 
  `e-mail`, 
  `link` 
FROM 
  cscart_sd_staff 
ORDER BY 
  `sort` ASC

Query time 0.00062

JSON explain

{
  "query_block": {
    "select_id": 1,
    "read_sorted_file": {
      "filesort": {
        "sort_key": "cscart_sd_staff.sort",
        "table": {
          "table_name": "cscart_sd_staff",
          "access_type": "ALL",
          "rows": 15,
          "filtered": 100
        }
      }
    }
  }
}