SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    9373, 5170, 5113, 5127, 5179, 5138, 5185, 
    5194, 5143, 5150, 5155, 5164, 5169, 
    5177, 5182
  )

Query time 0.00038

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "7.02"
    },
    "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": 15,
      "rows_produced_per_join": 15,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "4.02",
        "eval_cost": "3.00",
        "prefix_cost": "7.02",
        "data_read_per_join": "88K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`webmarco`.`cscart_categories`.`parent_id` in (9373,5170,5113,5127,5179,5138,5185,5194,5143,5150,5155,5164,5169,5177,5182))"
    }
  }
}