SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    3161, 3162, 3163, 3164, 3165, 3166, 3167, 
    3168, 3169, 3170, 3171, 3172, 3173, 
    3174, 3175, 3176, 3177, 3724, 3728
  )

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "9.02"
    },
    "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": 20,
      "rows_produced_per_join": 20,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "5.02",
        "eval_cost": "4.00",
        "prefix_cost": "9.02",
        "data_read_per_join": "118K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`webmarco`.`cscart_categories`.`parent_id` in (3161,3162,3163,3164,3165,3166,3167,3168,3169,3170,3171,3172,3173,3174,3175,3176,3177,3724,3728))"
    }
  }
}