Depends on how many servers. Facebook, Google, Amazon et al will gladly throw more hardware at a specific bottleneck. On the other hand, for more systemic kinds

Depends on how many servers. Facebook, Google, Amazon et al will gladly throw more hardware at a specific bottleneck. On the other hand, for more systemic kinds of slowness, even a 0.1% improvement translates into far more savings in hardware than the cost in developer salaries. When one cost is tied to scale and the other is relatively constant, a lot of tradeoffs are different for the big players than they are for smaller ones.