right down alley
(right) down (one's) alley
Something that one is or would be very interested in. A variant of the more common phrase "(right) up (one's) alley." Lou loves baseball, so you should definitely invite him to a game—it would be right down his alley. I love science, so studying medicine is down my alley.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
right down someone's alleyand right up someone's alley
Fig. ideally suited to one's interests or abilities. Skiing is right down my alley. I love it. This kind of thing is right up John's alley.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.