SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    5344, 5259, 5349, 5217, 5045, 5097, 5070, 
    8786, 5242, 5370, 5374, 5381, 5364, 
    5387, 8785, 5399, 5253, 5266, 8788, 
    5014, 5407, 5273, 4988, 5341, 5390, 
    5118, 4973, 4946, 4911, 5355, 5394, 
    5409, 5412, 5419, 5425
  )

Query time 0.00049

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "22.25"
    },
    "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": 53,
      "rows_produced_per_join": 53,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "11.65",
        "eval_cost": "10.60",
        "prefix_cost": "22.25",
        "data_read_per_join": "314K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`webmarco`.`cscart_categories`.`parent_id` in (5344,5259,5349,5217,5045,5097,5070,8786,5242,5370,5374,5381,5364,5387,8785,5399,5253,5266,8788,5014,5407,5273,4988,5341,5390,5118,4973,4946,4911,5355,5394,5409,5412,5419,5425))"
    }
  }
}