SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    4808, 4431, 4525, 4334, 4257, 4551, 4299, 
    4003, 4254, 5264, 4746, 5597, 5256, 
    4418, 5270, 4693, 4903, 5968, 4933
  )

Query time 0.00067

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "58.31"
    },
    "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": 143,
      "rows_produced_per_join": 143,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "29.71",
        "eval_cost": "28.60",
        "prefix_cost": "58.31",
        "data_read_per_join": "847K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`webmarco`.`cscart_categories`.`parent_id` in (4808,4431,4525,4334,4257,4551,4299,4003,4254,5264,4746,5597,5256,4418,5270,4693,4903,5968,4933))"
    }
  }
}