That's the difference between web development, "web2.0-style", and engineering. A web developer, when experiencing lag, will just add another AWS instance. An engineer will figure out where things are inefficient, and work against that inefficiency. You would be surprised how much of a performance boost you can get just by having good server-side pre-caching.

Also, consider that a lot of the lag you experience in the web today is actually caused client-side by excessive use of JS.