SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    9979, 9993, 9978, 9994, 9966, 9984, 9983, 
    9982, 9986, 9992, 9977, 9971, 10125, 
    10127, 10128, 10129, 10130, 10131
  )

Query time 0.00063

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "8.62"
    },
    "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": 19,
      "rows_produced_per_join": 19,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "4.82",
        "eval_cost": "3.80",
        "prefix_cost": "8.62",
        "data_read_per_join": "112K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`webmarco`.`cscart_categories`.`parent_id` in (9979,9993,9978,9994,9966,9984,9983,9982,9986,9992,9977,9971,10125,10127,10128,10129,10130,10131))"
    }
  }
}