"Facebook is updating tens of thousands of servers with every push. "Rolling back" a release would effectively take as long as a regular push and could contribute to problems if they're found."
Absolutely not. A lot of places get around this with a simple symlink switch. You keep N older releases. So it might be /code/releases with various datestamped releases...and /code/releases/current points to the currently running one. Want to rollback? Point current to one older. Done.
Presumably the 1.5gb facebook binary is deployed as a daemon listening on port 80. Seems unlikely that they are cgi-ing a new process for each request.
