What about state belonging to the older code, updating http handlers, user sessions, etc, on production? While living-in-the-image seems admirable, I always wo

What about state belonging to the older code, updating http handlers, user sessions, etc, on production? While living-in-the-image seems admirable, I always wondered how it blends with real production and real ops. The only thing I heard about this is Paul Graham's story on fixing particular bug in viaweb while talking to the user, but that's just one story from 90s. Would be great to hear more with regard to more modern setup.