Comment by alnwlsn

I'd probably put the typical smart switch hardware/software stack at around 0.25 seconds. Maybe you can but I don't think I'd try to rely on anything much faster than that.

If you did, I would go in the custom firmware for the smart switch direction. A lot of them are just an ESP32 inside, and you could probably get to 0.001 seconds that way (but you are switching AC which cycles on the order of 0.02 seconds, so whatever)