SELECT 
  category_id, 
  parent_id 
FROM 
  categories 
WHERE 
  parent_id IN(
    1611, 1609, 21099, 1608, 1612, 2883, 
    1604, 1605, 1602, 1606, 10395, 1610, 
    1575, 1603, 4871
  )

Query time 0.00124

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "4.28"
    },
    "table": {
      "table_name": "categories",
      "access_type": "range",
      "possible_keys": [
        "parent"
      ],
      "key": "parent",
      "used_key_parts": [
        "parent_id"
      ],
      "key_length": "3",
      "rows_examined_per_scan": 18,
      "rows_produced_per_join": 18,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "2.48",
        "eval_cost": "1.80",
        "prefix_cost": "4.28",
        "data_read_per_join": "47K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`goimagine`.`categories`.`parent_id` in (1611,1609,21099,1608,1612,2883,1604,1605,1602,1606,10395,1610,1575,1603,4871))"
    }
  }
}