SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    356, 10667, 1584, 344, 394, 2404, 443, 
    1936, 1907, 990, 930, 1498, 341, 327, 
    715, 2171, 2178, 2373, 2433, 2465, 2577, 
    2591, 2611, 2615, 9692, 9830, 9840, 
    9844, 9926, 9936, 10631, 10632, 10633
  )

Query time 0.00119

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "69.53"
    },
    "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": 171,
      "rows_produced_per_join": 171,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "35.33",
        "eval_cost": "34.20",
        "prefix_cost": "69.53",
        "data_read_per_join": "1013K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`webmarco`.`cscart_categories`.`parent_id` in (356,10667,1584,344,394,2404,443,1936,1907,990,930,1498,341,327,715,2171,2178,2373,2433,2465,2577,2591,2611,2615,9692,9830,9840,9844,9926,9936,10631,10632,10633))"
    }
  }
}