Before you invest in a CDN

The gap between knowing this and actually doing it is where most teams lose ground. Before you spend anything on a CDN, it is worth confirming a few things are already true.

Performance work is mostly subtraction, which makes it unpopular and effective. Check it against what you would want a competitor's site to get wrong.

Prerequisites

• You can describe the outcome you want in one sentence
• Someone owns it after the work is done
• Distance to the server is real latency
• You have a way to tell whether it worked

Warning signs

A CDN also absorbs traffic spikes. The teams that handle this well are rarely the ones with the biggest budgets. Anything you cannot measure here, you are deciding by taste, which is fine as long as everyone knows it.

Static sites benefit almost for free. This is the sort of thing that compounds, quietly, in both directions. Anything you cannot measure here, you are deciding by taste, which is fine as long as everyone knows it.

In practice

Speed is a feature people notice only in its absence, and then they leave rather than complain. Three things worth confirming about a CDN before you move on:

• Someone can say what the current setup is without going to look
• Static sites benefit almost for free — and you know whether that is true here
• There is a way to tell whether the last change to this helped

Worth checking on your own setup before it becomes someone else's problem to fix.