The Cost Envelope

1. The Third Envelope

The estimation module taught you to compute two envelopes before committing to a design: how much traffic the system has to absorb, and how much data it has to hold. There is a third, and most engineers never compute it.

What does this design cost per month?

The number matters for a reason that has nothing to do with saving money. Cost is the constraint that quietly decides which designs are allowed to exist