SELECT 
  category_id, 
  parent_id 
FROM 
  ushop_categories 
WHERE 
  parent_id IN(
    394, 403, 402, 401, 400, 399, 398, 397, 
    396, 395, 385, 393, 392, 391, 390, 389, 
    388, 387, 386
  ) 
  AND category_id != 264

Query time 0.00223

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "13.31"
    },
    "table": {
      "table_name": "ushop_categories",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "parent",
        "p_category_id"
      ],
      "key": "parent",
      "used_key_parts": [
        "parent_id"
      ],
      "key_length": "3",
      "rows_examined_per_scan": 19,
      "rows_produced_per_join": 19,
      "filtered": "100.00",
      "index_condition": "(`marketplace`.`ushop_categories`.`parent_id` in (394,403,402,401,400,399,398,397,396,395,385,393,392,391,390,389,388,387,386))",
      "cost_info": {
        "read_cost": "11.41",
        "eval_cost": "1.90",
        "prefix_cost": "13.31",
        "data_read_per_join": "61K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`marketplace`.`ushop_categories`.`category_id` <> 264)"
    }
  }
}