A short guide to system design reviews

There is no clever trick in this one, just a handful of decisions worth making deliberately. Everything we would tell a client about system design reviews in the time it takes to drink a coffee.

Most systems fail at the seams rather than inside any one component. Doing this properly once is usually cheaper than doing it approximately three times.

What is actually at stake

An hour of review before the build saves weeks of rework. In practice this is a scheduling problem more than a technical one. If it only works because one person remembers to do something, it does not work yet.

How to approach it

Write the design down. This is the sort of thing that compounds, quietly, in both directions. Doing this properly once is usually cheaper than doing it approximately three times.

What to watch for

Invite the person who will be on call for it. The cost of getting this wrong is rarely visible on the day it happens. Most teams find the first pass takes an afternoon and the maintenance takes minutes a month.

The short version

The right architecture for a team of three is the wrong one for a team of thirty, and vice versa. Three things worth confirming about system design reviews before you move on:

• Someone can say what the current setup is without going to look
• An hour of review before the build saves weeks of rework — and you know whether that is true here
• There is a way to tell whether the last change to this helped

Pick the one that would hurt most if it failed, and start there.