Scaling in and scaling out versus scaling up and scaling down

You've worked nights and weekends on your site. D-day has finally come, and your site has gone live. It's up and running, and people are starting to use it. You come back the next day, and even more, traffic is hitting. On the third day, you look at the stats and realize that you have a problem – too many people are signing up and using your service. While this is an excellent problem, you better act fast, or the site will start throttling, and the user experience will go down or be non-existent. But the question now is, how do you scale? Scalability challenges are encountered by IT organizations all over daily. It is difficult to predict demand and traffic for many applications, especially internet-facing applications. Therefore, it is difficult to predict how much storage capacity, compute power, and bandwidth will be needed. So when you reach the limits of your deployment, how do you increase capacity? If...