SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    35699, 28976, 35711, 32843, 7377, 7378, 
    1700, 2533, 14424, 14434, 1697, 1699, 
    2780, 2675, 2674, 2680, 982, 3653, 28392, 
    2532, 2647, 894, 14435, 6764
  )

Query time 0.00043

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "6.06"
    },
    "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": 28,
      "rows_produced_per_join": 28,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "3.26",
        "eval_cost": "2.80",
        "prefix_cost": "6.06",
        "data_read_per_join": "72K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`maniamall_cscart`.`cscart_categories`.`parent_id` in (35699,28976,35711,32843,7377,7378,1700,2533,14424,14434,1697,1699,2780,2675,2674,2680,982,3653,28392,2532,2647,894,14435,6764))"
    }
  }
}

Result