Eric Lindvall responding to Brent Simmons about scaling web apps:
A fundamental part of scaling a growing service is that you’re never done. If you are continuing to grow, there will always be more and different bottlenecks that crop up. There will never be a piece of technology or a style of development or architecture that will mitigate that.
It is too easy to beat yourself up over deploying a solution that did not meet every possible combination of scaling requirements over the next five years. For a fast growing service not only is that ok, it is probably the only way to move fast enough to keep up.