On a student platform we show, on every page, a random user in the upper right corner. Because we have over 11.000 users, the database has to select all matching users and sort them by
random(). Thats very expensive and one of the longest running queries in the current version. And because we are currently redeveloping the whole platform, I decided to try something different for the random user. The user must not be really random, it should be enough to just display a different user every time the page is displayed. My idea was to implement a ringbuffer in SQL and forward the pointer to the next user in the buffer if we need to search the next random user.