SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    3085, 3091, 3109, 3279, 3207, 9017, 3191, 
    3254, 3095, 3102, 3305, 3216, 3138, 
    3236, 3313, 3144, 3240, 3319, 3152, 
    3324, 3156, 3333, 3178, 3336, 3185, 
    3199, 3247, 3267, 3272, 3716
  )

Query time 0.00049

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "17.04"
    },
    "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": 40,
      "rows_produced_per_join": 40,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "9.04",
        "eval_cost": "8.00",
        "prefix_cost": "17.04",
        "data_read_per_join": "237K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`webmarco`.`cscart_categories`.`parent_id` in (3085,3091,3109,3279,3207,9017,3191,3254,3095,3102,3305,3216,3138,3236,3313,3144,3240,3319,3152,3324,3156,3333,3178,3336,3185,3199,3247,3267,3272,3716))"
    }
  }
}