SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    5344, 5349, 5370, 5374, 5381, 5364, 5387, 
    5399, 5407, 5355, 5394, 5409, 5412, 
    5419, 5425
  )

Query time 0.00063

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "9.82"
    },
    "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": 22,
      "rows_produced_per_join": 22,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "5.43",
        "eval_cost": "4.40",
        "prefix_cost": "9.83",
        "data_read_per_join": "130K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`webmarco`.`cscart_categories`.`parent_id` in (5344,5349,5370,5374,5381,5364,5387,5399,5407,5355,5394,5409,5412,5419,5425))"
    }
  }
}