SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    19349, 19563, 21094, 3128, 21146, 3309, 
    3141, 20820, 21383, 3336, 23735, 21341, 
    3166, 3163, 3167, 3354, 3353, 3164, 
    3165, 3355, 8093, 20826, 3343, 3347, 
    3346, 3344, 3348, 3345
  )

Query time 0.00051

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "7.96"
    },
    "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": 38,
      "rows_produced_per_join": 38,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "4.16",
        "eval_cost": "3.80",
        "prefix_cost": "7.96",
        "data_read_per_join": "98K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`maniamall_cscart`.`cscart_categories`.`parent_id` in (19349,19563,21094,3128,21146,3309,3141,20820,21383,3336,23735,21341,3166,3163,3167,3354,3353,3164,3165,3355,8093,20826,3343,3347,3346,3344,3348,3345))"
    }
  }
}

Result