in the blink of an eye

So quickly as to seem almost imperceptible (i.e., in the space of time it takes a person to blink).

速度快得几乎感觉不到(也就是说，眨眼的时间内)。一眨眼，瞬间

In the blink of an eye, he was gone.

一眨眼他就不见了。

Working on Wall Street, you get used to massive financial changes happening in the blink of an eye.

在华尔街工作，你会习惯在眨眼之间发生的巨大金融变化。