pg: I have fair bit of lisp dev experience. If, as a weekend project, I modified the HN src to use postgres and memcache would you consider using it in production? Obviously, I don't expect carte blanche prior agreement, but I wouldn't want to invest the time unless I thought it was plausible the work could actually help.

I would expect it to solve most of your performance problems for the foreseeable future (at the very least, by letting you scale horizontally and move the DB, frontends, and memcaches to separate boxes - plus ending memory leaks/etc by moving most of the data off the MzScheme heap).

The obvious downside is that it would use your (or someone at YC's) time. First to merge the changes I make to http://ycombinator.com/arc/arc3.tar into the production code, then to buy/setup some extra boxes and do the migration. We're probably talking, roughly, a day. It also has the unfortunate side effect of costing HN's src some of its pedagogical value, since it adds external dependencies and loses 'purity'.

Been looking for an excuse to learn arc for a while now ...