I wrote what was most likely the very first real time internet auction with browser front end some time I think in 94. For backend I just wrote a little native webserver that along with handling http also implemented all business rules. It was business to business and replaced dial-in phone based system working on mainframe.

Not sure about impact, most likely miniscule and I have designed and implemented much bigger software systems later on but for some unknown reason I feel particularly warm about that auction thingy.