SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    265, 267, 297, 298, 276, 268, 288, 271, 
    308, 299, 282, 269, 277, 286, 294, 295, 
    266, 311, 278, 270, 300, 292, 301, 317, 
    322, 305, 309, 296, 302, 323, 318, 325, 
    303, 314, 319, 310, 326, 321
  )

Query time 0.00050

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "6.64"
    },
    "table": {
      "table_name": "cscart_categories",
      "access_type": "ALL",
      "possible_keys": [
        "parent"
      ],
      "rows_examined_per_scan": 59,
      "rows_produced_per_join": 59,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "0.74",
        "eval_cost": "5.90",
        "prefix_cost": "6.64",
        "data_read_per_join": "153K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`wearethehelpful_scalesta_net`.`cscart_categories`.`parent_id` in (265,267,297,298,276,268,288,271,308,299,282,269,277,286,294,295,266,311,278,270,300,292,301,317,322,305,309,296,302,323,318,325,303,314,319,310,326,321))"
    }
  }
}