I don't do web scalability (I'm in HPC), but being a sysadmin, doing more with less is the name of the game. I think the absolute best answer is think about it

I don't do web scalability (I'm in HPC), but being a sysadmin, doing more with less is the name of the game. I think the absolute best answer is think about it now, but worry about it when you get there That is to say, you should be conscious of how your decisions will affect you down the road, but you ultimately have to make a risk assessment whether to pay now or pay later. How likely, really, are you going to run into that problem later? When you do run into scalability problems, you have a very clear bottleneck. If you don't, spend a few hours figuring out what the problem is. Fix that first. This is going to shift your bottleneck. CPU, Network, Disk. They're just going to rotate around as you fix one, the next one becomes the issue. You can't ever fix all your bottlenecks, you can just shift them around until it's "good enough." Fixing it more won't justify the cost, so you just deal with how it is, or you bring in a new solution that promises to solve your problems. Put it this way -- If your first problem is how to optimize your quarter of a million dollar piece of equipment, you're probably in a pretty good spot. Otherwise, get there first.