The phrase "down one's alley" means something that is within someone's area of expertise or interest. There are several other expressions that convey a similar meaning. For instance, "up one's street" is an alternative that can be used to describe something that suits someone's skills or interests perfectly. "In one's wheelhouse" is another synonym, particularly in fields that involve a particular set of skills, experience, or expertise. "Right up one's alley" or "in one's element" are other succinct expressions that mean the same thing. Similarly, "in one's comfort zone" is an idiom that conveys the idea that someone is doing something they find easy or familiar.
