The network of sites that make up StackExchange, which includes StackOverflow, is now ranked 54th for traffic in the world; they have 110 sites and are growing at a rate of 3 or 4 a month; 4 million users; 40 million answers; and 560 million pageviews a month. This is with just 25 servers. For everything. That’s high availability, load balancing, caching, databases, searching, and utility functions. All with a relative handful of employees. Now that’s quality engineering.
» Todd Hoff | highscalability.com