SELECT 
  id_path 
FROM 
  cscart_categories 
WHERE 
  category_id IN (2397, 2398, 2399, 2401, 2402)

Query time 0.00046

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "7.03"
    },
    "table": {
      "table_name": "cscart_categories",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "p_category_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "category_id"
      ],
      "key_length": "3",
      "rows_examined_per_scan": 5,
      "rows_produced_per_join": 5,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "6.03",
        "eval_cost": "1.00",
        "prefix_cost": "7.03",
        "data_read_per_join": "29K"
      },
      "used_columns": [
        "category_id",
        "id_path"
      ],
      "attached_condition": "(`webmarco`.`cscart_categories`.`category_id` in (2397,2398,2399,2401,2402))"
    }
  }
}