SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    235, 203, 167, 221, 168, 169, 204, 174, 
    197, 166, 208, 236, 199, 178, 212, 240, 
    238, 211, 237, 414, 260, 250, 220, 224
  )

Query time 0.00005

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "14.16"
    },
    "table": {
      "table_name": "cscart_categories",
      "access_type": "ALL",
      "possible_keys": [
        "parent"
      ],
      "rows_examined_per_scan": 51,
      "rows_produced_per_join": 51,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "3.96",
        "eval_cost": "10.20",
        "prefix_cost": "14.16",
        "data_read_per_join": "208K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`44mm_ru`.`cscart_categories`.`parent_id` in (235,203,167,221,168,169,204,174,197,166,208,236,199,178,212,240,238,211,237,414,260,250,220,224))"
    }
  }
}