instantly vs straight off

instantly and straight off both are adverbs.

Word	Noun	Adjective	Verb	Adverb
instantly	No	No	No	Yes
straight off	No	No	No	Yes

As adverbs, instantly and straight off are synonyms defined as:

instantly and straight off: without delay or hesitation; with no time intervening

Other synonyms of instantly include at once, directly, forthwith, immediately, like a shot, now, right away, straightaway.

instantly (adverb)	straight off (adverb)
without delay or hesitation; with no time intervening	without delay or hesitation; with no time intervening
without any delay