right away vs instantly

right away and instantly both are adverbs.

Word	Noun	Adjective	Verb	Adverb
right away	No	No	No	Yes
instantly	No	No	No	Yes

As adverbs, right away and instantly are synonyms defined as:

right away and instantly: without delay or hesitation; with no time intervening

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

right away (adverb)	instantly (adverb)
without delay or hesitation; with no time intervening	without delay or hesitation; with no time intervening
at once (usually modifies an undesirable occurrence)	without any delay