Some domains suit the relational database model better than others. If he was doing a huge amount of machine learning-type stuff he might have a different archi

Some domains suit the relational database model better than others. If he was doing a huge amount of machine learning-type stuff he might have a different architecture. Then again, given that he (like most people, myself included) has a lot of RDB experience, he designed his application around what RDBs do well. Perhaps if he had 10+ years of experience with distributed hash tables he might have designed a site with a different feature set.