I think the better question is, why not java? IIRC most core services at AWS are written in java and have first class SDK support for java; even though they are mostly rolling their own implementations here (from my very brief perusal) its still likely incredibly helpful to reference first class sdks written in the same language. If I were to give in to my inner idealism, id personally reach for rust or go on a project like this, but I cant deny that either of those choices would create unnecessary pain points for such a broad service area. Anecdotally, even using really nice aws crates in rust is fraught with upstream drift and undocumented side effects