SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    298, 301, 303, 309, 312, 333, 375, 392, 
    399, 403, 406, 412, 414, 417, 436
  )

Query time 0.00043

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "30.49"
    },
    "table": {
      "table_name": "cscart_categories",
      "access_type": "ALL",
      "possible_keys": [
        "parent"
      ],
      "rows_examined_per_scan": 125,
      "rows_produced_per_join": 83,
      "filtered": "67.20",
      "cost_info": {
        "read_cost": "13.69",
        "eval_cost": "16.80",
        "prefix_cost": "30.49",
        "data_read_per_join": "343K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`cscart`.`cscart_categories`.`parent_id` in (298,301,303,309,312,333,375,392,399,403,406,412,414,417,436))"
    }
  }
}