某ヘ社ならメンテナンス画面を表示させるのもコマンドいっぱつ https://devcenter.heroku.com/articles/maintenance-mode #ステマ
devcenter.heroku.comMaintenance Mode | Heroku Dev CenterHeroku’s maintenance mode feature serves a static page to all visitors, allowing developers to perform maintenance tasks that require the absence of incoming traffic.