In the blink of an eye

very quickly:

Software that would do lots of boring calculations in the blink of an eye.
Richard was a little shocked to see her go from shy and demure to forthright and direct in the blink of an eye.
Dinner went by reasonably quickly, and in the blink of an eye, they were fast asleep, except for one.
He looks like a picture, frozen in time, one instant that happened in the blink of an eye, unnoticed and uncared for by the rest of the universe.