Cost-aware architecture

The core idea

The redirect path fits inside a single database's measured capacity, which capacity planning established a lesson ago. That settles whether one machine can do the work. It leaves a different question open: what will serving those redirects cost, and which parts of the design are worth paying for?

Cost is a requirement like any other. It has a number, it can be measured, and it can be broken. The difference is that nobody writes it on the brief, so it gets discovered on an invoice.