SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    276, 66, 7, 597, 1, 36, 226, 325, 400, 29, 
    41, 59, 614, 58, 57, 151, 257, 170, 181, 
    436, 639, 660, 666
  )

Query time 0.00059

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "57.96"
    },
    "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": 116,
      "rows_produced_per_join": 116,
      "filtered": "100.00",
      "index_condition": "(`dbggbern`.`cscart_categories`.`parent_id` in (276,66,7,597,1,36,226,325,400,29,41,59,614,58,57,151,257,170,181,436,639,660,666))",
      "cost_info": {
        "read_cost": "46.36",
        "eval_cost": "11.60",
        "prefix_cost": "57.96",
        "data_read_per_join": "464K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ]
    }
  }
}