SELECT 
  category_id, 
  parent_id 
FROM 
  ushop_categories 
WHERE 
  parent_id IN(
    503, 504, 505, 353, 359, 506, 349, 507, 
    508, 509, 510, 511, 521, 512, 513, 514, 
    515, 516, 517, 518, 519, 520
  ) 
  AND category_id != 264

Query time 0.00106

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "15.41"
    },
    "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": 22,
      "rows_produced_per_join": 22,
      "filtered": "100.00",
      "index_condition": "(`marketplace`.`ushop_categories`.`parent_id` in (503,504,505,353,359,506,349,507,508,509,510,511,521,512,513,514,515,516,517,518,519,520))",
      "cost_info": {
        "read_cost": "13.21",
        "eval_cost": "2.20",
        "prefix_cost": "15.41",
        "data_read_per_join": "71K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`marketplace`.`ushop_categories`.`category_id` <> 264)"
    }
  }
}