I'm quite new to Express.js and one of the things that surprised me more at first, compare to other servers such as Apache or IIS, is that Express.js server crashes every time it encounters an uncatched exception or some error turning down the site and making it accessible for users. A terrible thing!
TypeError: Cannot call method 'replace' of undefined
The main difference between Apache and nodejs in general is that Apache forks a process per request while nodejs is single threaded, hence if an error occurs in Apache then the process handling that request will crash while the others will continue to work, in nodejs instead the only thread goes down.
In my projects I use monit to check memory/cpu (if nodejs takes to much resources of my vps then monit will restart nodejs) and daemontools to be sure nodejs is always up and running.