Wiktionary
be right back
phr. Used to indicate the speaker will return in a moment. Often abbreviated in online slang as ''brb''.
Wikipedia
Be Right Back (Black Mirror)
"Be Right Back" is the first episode of the second series of Black Mirror. It starred Hayley Atwell and Domhnall Gleeson, and was first shown on Channel 4 on 11 February 2013. The episode was written by series creator Charlie Brooker.
Usage examples of "be right back".
By the time she's got a life-belt on her, and is being hustled into a boat, with a well-drilled lot of artistes doing the hysterical stunt on deck, why--she ought to be right back where she was in May, 1915.
In fact, depending on what hardware Loemanako left aboard the ship, he may be right back with a tactical nuclear warhead.
Rollins, tell him I just have to load this and I'll be right back.