SELECT 
  addon 
FROM 
  cscart_addons 
WHERE 
  unmanaged = 1 
  AND status = 'A' 
ORDER BY 
  priority

Query time 0.00036

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "16.86"
    },
    "ordering_operation": {
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "1.00"
      },
      "table": {
        "table_name": "cscart_addons",
        "access_type": "ALL",
        "rows_examined_per_scan": 66,
        "rows_produced_per_join": 1,
        "filtered": "1.52",
        "cost_info": {
          "read_cost": "15.66",
          "eval_cost": "0.20",
          "prefix_cost": "15.86",
          "data_read_per_join": "1K"
        },
        "used_columns": [
          "addon",
          "status",
          "priority",
          "unmanaged"
        ],
        "attached_condition": "((`db_emaika1`.`cscart_addons`.`unmanaged` = 1) and (`db_emaika1`.`cscart_addons`.`status` = 'A'))"
      }
    }
  }
}