in half a second

1 立即

present immediate instant slap-bang foothot away instantly thereon straightway subito immediateness at lightning speed with lightning speed at a clap at one clap at a word at one word down on the nail on the instant without a moment's thought at a moment's notice in less than no time lose no time on the nail in tracks right now in a minute in an instant in a flash then and there off the bat there and then the next moment

2 很快

quick shortly pronto before one knows it like nobody's business very soon in a short time like wildfire