What, you mean with "hot deployment" of your changes?
Well, even in Play Framework 1.0 in 2009 there was hot reloading. Edit a file, refresh your browser => it's there.
On the Atari ST you didn't even have to hit reload, the webpage reloaded automatically as soon as you saved your file. No need to alt-tab even, just keep webpage open next to your editor. Now get off my lawn.