instantly vs like a shot

instantly and like a shot both are adverbs.

Word	Noun	Adjective	Verb	Adverb
instantly	No	No	No	Yes
like a shot	No	No	No	Yes

As adverbs, instantly and like a shot are synonyms defined as:

instantly and like a shot: without delay or hesitation; with no time intervening

Other synonyms of instantly include at once, directly, forthwith, immediately, now, right away, straight off, straightaway.

instantly (adverb)	like a shot (adverb)
without delay or hesitation; with no time intervening	without delay or hesitation; with no time intervening
without any delay