Few questions:

1)When we say "We can compute a unique hash (e.g., MD5 or SHA256, etc.) of the given URL" . There still are chances that hash is not unique, i believe it would be a good call out. And this level should suffice for the technical interview at least.

2)What is the exact problem we are emphasising when we say what if parts of url are URL encoded? e.g., http://www.designgurus.org/distributed.php?id=design , and http://www.designgurus.org/distributed.php%3Fid%3Ddesign

Does this mean that if user wants to shorten both of these , we should just tell that its already shortened for this user. Also, i don't see any solution to this problem in the Workaround section.