SELECT 
  category_id, 
  parent_id 
FROM 
  categories 
WHERE 
  parent_id IN(
    12955, 4939, 8274, 4937, 4932, 4940, 
    4934, 11030
  )

Query time 0.00055

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "2.44"
    },
    "table": {
      "table_name": "categories",
      "access_type": "range",
      "possible_keys": [
        "parent"
      ],
      "key": "parent",
      "used_key_parts": [
        "parent_id"
      ],
      "key_length": "3",
      "rows_examined_per_scan": 9,
      "rows_produced_per_join": 9,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "1.54",
        "eval_cost": "0.90",
        "prefix_cost": "2.44",
        "data_read_per_join": "23K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`goimagine`.`categories`.`parent_id` in (12955,4939,8274,4937,4932,4940,4934,11030))"
    }
  }
}