The silicon microchips themselves might be cheap (relative to times past, anyway), but CPU cycles are not cheap. Every CPU cycle consumes clock time. Clock time is latency. A wasteful application makes its users wait longer than they need to, and if there’s anything users hate, it’s waiting. For web systems, latency in the application has a dual effect. The added processing directly increases the burden on the application servers themselves. Suppose that an application takes just 250 milliseconds of extra processing per transaction. If the system processes a million transactions a day, that extra 250 milliseconds per transaction makes for an extra 69.4 hours of compute time every day. Assuming an 80% load factor on each server, you’ll need four additional servers to handle this load.

Michael T. Nygard