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.
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.