For some project, I wrote this algoritem in Java to parse a lot of XML files and save data to database. It needs to have some tricks and optimisations to run in acceptable time. I did it and in average, it run for 8-10 minutes.

After I left company they got new guy. And he didn't know Java so they switched to PHP and rewrote the whole project. He did algorithm his way. After rewrite it run around 8 hours.

I was really proud of myself and shocked they consider it acceptable.