The architecture of AOLserver was ahead of its time back in the day. Using threads rather than processes like Apache meant that all the threads could share a connection pool to the database. And the built-in Tcl support, while idiosyncratic (everything is a string!), was good enough for most web backend work.

Phil Greenspun wrote a book about architecting web applications ("web scale" two decades before that became a meme) that was, and still is, available for free online (https://philip.greenspun.com/panda/ ).

Greenspun had a company, ArsDigita, that created a big framework for building web applications, ACS (ArsDigita Community System), and there was an open source version of it called OpenACS that AFAIU was basically a port from Oracle to PostgreSQL (the recently released PostgreSQL 7.0 had just acquired sufficient capabilities to be usable as an Oracle substitute for ACS) but otherwise pretty much the same. Back then when a "web framework" basically meant a hodgepodge of spaghetti PHP, this was beyond awesome.

I used OpenACS to create some intranet reporting systems as a summer intern back in the day, and it was pretty good, the code was decently well structured and understandable. Though in retrospect I pity whoever had to maintain that tech stack after I left; my best guess is the system ran for a few years until they killed it off as nobody understood it since OpenACS was very much off the beaten track.