[easp]

Capacity planning isn't just hard, it is costly. You have to profile every new version of your app, and every new version of the software you depend on. You have to update your planning models with that data, and then you have to provision extra hardware to handle whatever traffic spikes you think you'll be faced with within your planning window. Most of the time, those resources will be idle, but you will still be paying for them. Plus in the face of an extraordinary event, you'll be giving users a degraded experience.

Using "the cloud" doesn't solve all those problems but your costs can track your needs more closely, and with less up-front investment. Rather than carefully planning revisions to your infrastructure you can build a new one test it, cut over to it, and then ditch the old one.

You should still profile your app under load so you can be confident that you can indeed scale up easily, but even that is easier. You can bring up a full-scale version to test for a day and then take it down again.

I'm not against capacity planning, but it has it's time and place.