Three myths about system design reviews

This is cheap to get right at the start and expensive to retrofit. A few things about system design reviews that get repeated more often than they get checked.

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.

“It only matters for big sites”

An hour of review before the build saves weeks of rework. None of that requires a large budget, only a decision and someone to own it. Write the reasoning down alongside the decision, because the reasoning is what changes first.

“We can deal with it after launch”

Sometimes true, usually expensive. It is worth being explicit about, because assumptions differ quietly.

“Our platform handles it”

Invite the person who will be on call for it. This is the sort of thing that compounds, quietly, in both directions. Budget a little time for it every quarter and it never becomes a project of its own.

The short version

Architecture is the set of decisions that are expensive to reverse, which is the only reason they deserve the name. Three things worth confirming about system design reviews before you move on:

• Someone can say what the current setup is without going to look
• a whiteboard photo is not a record — and you know whether that is true here
• There is a way to tell whether the last change to this helped

None of this needs a rewrite. Most of it is a morning's work once someone decides to do it.