> That totally depends on your available toolset and experience.
That's either ignorant or boastful (or both). Any decent programmer will admit that they can't build a good and scalable anything in a week from scratch.
If you count your "toolset" as an entire framework that does what you want already, then sure, maybe it's possible. Otherwise you're just being foolish.
For a complex system, like an OS or a browser.
This is a bloody social news site, as trivial an application as it gets.
One man can write a half-decent one in a week.
And for ramping it up, even the scaling roadblocks and tricks are old news by now to the web building community in general.