At Subway (the sandwich company) they got high speed ovens which toast bread in like 20 seconds. I always wondered what magic is inside to be that quick.Today I found out that you can even buy those ovens if you have a need for them. Like this one: https://www.turbochef.com/product/bullet/
And the magic they use: hot air as well as microwaves.
Before you think about buying one: it'll cost you about US$10k, and the Japanese version uses 200V and 30A (resp. 400V/16A for those in 230V countries).