SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    3105, 3269, 7769, 6552, 6536, 2910, 7862, 
    5684, 6473
  )

Query time 0.00062

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "51.10"
    },
    "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": 125,
      "rows_produced_per_join": 125,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "26.10",
        "eval_cost": "25.00",
        "prefix_cost": "51.10",
        "data_read_per_join": "741K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`webmarco`.`cscart_categories`.`parent_id` in (3105,3269,7769,6552,6536,2910,7862,5684,6473))"
    }
  }
}

Result

category_id parent_id
2912 2910
2913 2910
2914 2910
2915 2910
2916 2910
2920 2910
2921 2910
2933 2910
2944 2910
3006 2910
3007 2910
3011 2910
3018 2910
3080 2910
3105 2910
3251 2910
3362 2910
3408 2910
3691 2910
4029 2910
5522 2910
3104 3105
3110 3105
3111 3105
3112 3105
3113 3105
3114 3105
3222 3105
3223 3105
3224 3105
3225 3105
3226 3105
3227 3105
3228 3105
3229 3105
3230 3105
3231 3105
3269 3105
9020 3105
9832 3105
5699 5684
6536 5684
6540 5684
7840 5684
6568 6473
6600 6473
6809 6473
6875 6473
6968 6473
7023 6473
7080 6473
7135 6473
7226 6473
7285 6473
7627 6473
7763 6473
7764 6473
7769 6473
7822 6473
10324 6473
6552 6536
7635 6536
7746 6536
7752 6536
7767 6536
7773 6536
7805 6536
7888 6536
7896 6536
7963 6536
7993 6536
8008 6536
8313 6536
8318 6536
8355 6536
8356 6536
8426 6536
6582 6552
6730 6552
6773 6552
6806 6552
6890 6552
6917 6552
6955 6552
6988 6552
7019 6552
7064 6552
7126 6552
7245 6552
7277 6552
7303 6552
7324 6552
7365 6552
7611 6552
7625 6552
7857 7769
7858 7769
7859 7769
7860 7769
7861 7769
7862 7769
7863 7769
7864 7769
7865 7769
7866 7769
7867 7769
7868 7769
7869 7769
7870 7769
7871 7769
7872 7769
7873 7769
7874 7769
7875 7769
7876 7769
7877 7769
7878 7769
7879 7769
7880 7769
7881 7769
7882 7769
7883 7769
8104 7769