I was under the impression that power mode switching took ~50 micro seconds, which means power savings modes toggle on an off between keystrokes. The problem h

I was under the impression that power mode switching took ~50 micro seconds, which means power savings modes toggle on an off between keystrokes. The problem here isn't awaking the CPU, but rather awaking the radios. If you don't turn on the radios, polling every 20 seconds shouldn't be a problem. I'd mix this approach with something like the Page Visibility API, so you don't fetch data unless the site is the active tab.