SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    9276, 9965, 9994, 9983, 2658, 9992, 266, 
    10491, 2653, 1695, 327, 2849, 10563
  )

Query time 0.00063

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "44.29"
    },
    "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": 108,
      "rows_produced_per_join": 108,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "22.69",
        "eval_cost": "21.60",
        "prefix_cost": "44.29",
        "data_read_per_join": "640K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`webmarco`.`cscart_categories`.`parent_id` in (9276,9965,9994,9983,2658,9992,266,10491,2653,1695,327,2849,10563))"
    }
  }
}

Result

category_id parent_id
327 266
341 266
344 266
356 266
394 266
443 266
715 266
930 266
990 266
1498 266
1584 266
1907 266
1936 266
2171 266
2178 266
2373 266
2404 266
2433 266
2465 266
2577 266
2591 266
2611 266
2615 266
9692 266
9830 266
9840 266
9844 266
9926 266
9936 266
10631 266
10632 266
10633 266
10667 266
328 327
1018 327
1438 327
1695 327
2528 327
2566 327
2567 327
2597 327
1696 1695
1697 1695
1698 1695
2568 1695
2599 1695
2602 1695
2656 2653
2658 2653
2721 2653
2760 2653
2761 2653
2797 2653
2804 2653
2853 2653
9965 2653
9967 2653
9968 2653
9980 2653
2657 2658
2661 2658
2671 2658
2695 2658
2722 2658
2724 2658
2729 2658
2763 2658
2767 2658
2769 2658
2789 2658
2800 2658
2812 2658
2822 2658
2829 2658
2837 2658
2843 2658
2849 2658
8851 2658
9250 2658
9257 2658
9276 2658
9574 2658
9990 2658
10562 2658
10563 2658
2859 2849
2868 2849
2878 2849
9277 9276
9966 9965
9971 9965
9977 9965
9978 9965
9983 9965
9986 9965
9992 9965
9994 9965
10125 9965
10127 9965
10128 9965
10129 9965
10130 9965
10131 9965
9984 9983
9993 9992
10662 10491