It'd be interesting to read a write up on the concepts used (such as the in memory database) and the server restart mechanism. It'd be hard to tell from the source for non Lisp programmers.
An in-memory database is pretty simple - it's just a bunch of hash tables.
A server restart mechanism is also pretty simple. Write a cron job that activates every few seconds to ps aux and grep for the server name, and if it's not there start the server. That won't catch server hangs rather than deaths, but that's exactly the problem that happened here.
