In 1994, amzn ran on a single solaris workstation. Same at the beginning of 1995. I can't comment after that.
we invented a system we called "almost in time", the basic principle of which was "no we don't have that in stock but we can get it for you really fast". this is why we had to write our own system, because all the existing inventory mgmt systems (at least at that time) assumed that you would have at least some stuff in stock.
I've had friends finding photos of their own bicycle locked in the street advertized in second hand platforms.