I prefer the bare minimum approach. That is, if you NEED the user resource to access the event (eg the primary key is like [user ID, event ID]) then nest it in

I prefer the bare minimum approach. That is, if you NEED the user resource to access the event (eg the primary key is like [user ID, event ID]) then nest it in the url. Otherwise if an object has its own ID and could otherwise be accessed independently why not just do so?