One of my clients had a TV commercial this weekend and contacted me about it a week before.
Because I already set the shop up with caching and failover it was not a problem, whereas they normally have about 8000 unique hits a day there were about 190,000 this weekend. There was a little more load, everything else held up quite well, speedy even.
I have seen it go otherwise where when there are 30% more hits the sites crash. (Yes you, magento). What do you guys do when a situation like this appears? Upgrade the VPS for more specs? Set up caching (memcached/redis etc)? Scale out to more servers? Cloudflare? And, why?