SELECT 
  id_path 
FROM 
  cscart_categories 
WHERE 
  category_id IN (
    338, 339, 345, 349, 350, 352, 359, 362, 
    369, 377, 378, 379, 381, 384, 388, 390, 
    391, 394
  )

Query time 0.00090

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "28.02"
    },
    "table": {
      "table_name": "cscart_categories",
      "access_type": "ALL",
      "possible_keys": [
        "PRIMARY",
        "p_category_id"
      ],
      "rows_examined_per_scan": 115,
      "rows_produced_per_join": 17,
      "filtered": "15.65",
      "cost_info": {
        "read_cost": "24.42",
        "eval_cost": "3.60",
        "prefix_cost": "28.02",
        "data_read_per_join": "48K"
      },
      "used_columns": [
        "category_id",
        "id_path"
      ],
      "attached_condition": "(`eshopuga_upgr_4122`.`cscart_categories`.`category_id` in (338,339,345,349,350,352,359,362,369,377,378,379,381,384,388,390,391,394))"
    }
  }
}