Quora once had an URL-shortener. Perhaps it still has it. Interestingly, when two different user accounts requested the shortened URL for the very same question, they would get two different shortened URLs. Hence, I assume that Quora would do something along the lines of concatenating the user ID and the question ID and then hash that concatenated string.
Does anyone know how Quora’s URL-shortener worked?
I searched, but found nothing. Obviously, this may be a commercial secret.
Note that Stack Exchange’s URL-shortener also provides a unique shortened URL for each user account. However, Stack Exchange’s URL-shortener is as simple as
https://xyz.stackexchange.com/q/questionID/userID, where the user ID is clearly visible and can be removed. No hashing is used. Hence, unlike Quora, Stack Exchange gives one the option to reveal who shared the link or not. Quora did (does?) not give one that option.