This is not strictly PHP, but it is about scalability, and every PHP programmer *ought* to be thinking about this stuff. Theo Schlossnagle of OmniTI (where I work as a web architect) has this slide deck posted about Scalable Internet Architectures.
Paul points out some highlights of the slides:
- Slide 7: "Lack of awareness of the other disciplines is bad."
- Slide 29: Know the difference between "premature optimization" and "necessary optimization".
- Slide 59: "Scaling is hard, performance is easier. Extremely high-performance systems tend to be easier to scale, because they don't have to SCALE as much."
- Slide 63: Combine this with slide 59, and you have the reason why you need to know your application responsiveness.