Introduction

The Front Door: How to Read This Module

The scaling capstone ended parked at a doorstep: at a million requests per second, the interesting questions stopped being about servers and became about the boundary: what gets in, what gets turned away, what gets answered without ever waking a server. This module is that boundary: nine patterns governing how traffic enters, gets policed, gets shaped, and: between your own services: how it flows internally.

Nine patterns sounds like a lot. Two facts shrink it.