SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    668, 667, 650, 590, 585, 583, 584, 558, 
    84, 557, 509, 501, 450, 448, 449, 440, 
    401, 415, 393, 3, 366, 352, 19, 347, 312, 
    311, 299, 21, 292, 261, 260, 49, 259, 
    64, 251, 234, 189, 245, 26, 219, 196, 
    188, 150, 107, 101, 100, 92, 89, 75, 73, 
    11, 38, 6, 17, 18, 214, 215, 285, 286
  )

Query time 0.00059

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "62.91"
    },
    "table": {
      "table_name": "cscart_categories",
      "access_type": "range",
      "possible_keys": [
        "parent"
      ],
      "key": "parent",
      "used_key_parts": [
        "parent_id"
      ],
      "key_length": "3",
      "rows_examined_per_scan": 107,
      "rows_produced_per_join": 107,
      "filtered": "100.00",
      "index_condition": "(`dbggbern`.`cscart_categories`.`parent_id` in (668,667,650,590,585,583,584,558,84,557,509,501,450,448,449,440,401,415,393,3,366,352,19,347,312,311,299,21,292,261,260,49,259,64,251,234,189,245,26,219,196,188,150,107,101,100,92,89,75,73,11,38,6,17,18,214,215,285,286))",
      "cost_info": {
        "read_cost": "52.21",
        "eval_cost": "10.70",
        "prefix_cost": "62.91",
        "data_read_per_join": "428K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ]
    }
  }
}