SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    2664, 2667, 2693, 2708, 2668, 2681, 2696, 
    2709, 2714, 2672, 2682, 2699, 2674, 
    2685, 2676, 2690, 2701, 2704, 2717
  )

Query time 0.00055

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "11.83"
    },
    "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": 27,
      "rows_produced_per_join": 27,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "6.43",
        "eval_cost": "5.40",
        "prefix_cost": "11.83",
        "data_read_per_join": "160K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`webmarco`.`cscart_categories`.`parent_id` in (2664,2667,2693,2708,2668,2681,2696,2709,2714,2672,2682,2699,2674,2685,2676,2690,2701,2704,2717))"
    }
  }
}