When a CDN is worth the effort

The version of this that works is simpler than the version most people imagine. A CDN is not free, and pretending otherwise leads to bad decisions.

Speed is a feature people notice only in its absence, and then they leave rather than complain. Budget a little time for it every quarter and it never becomes a project of its own.

When it is worth it

Distance to the server is real latency. The teams that handle this well are rarely the ones with the biggest budgets. It is the sort of thing that looks like polish right up until it costs you an enquiry.

When it is not

If nothing downstream depends on it and nobody is complaining, it can wait. The reasoning matters more than the rule, because the rule has exceptions.

How to decide

Static sites benefit almost for free. Getting it slightly wrong is survivable. Ignoring it entirely is not. Budget a little time for it every quarter and it never becomes a project of its own.

In practice

Real-world numbers from actual visitors matter more than a score produced on a fast laptop. Three things worth confirming about a CDN before you move on:

• Someone can say what the current setup is without going to look
• Distance to the server is real latency — and you know whether that is true here
• There is a way to tell whether the last change to this helped

If you are not sure where your systems currently stand on this, it takes us about an hour to find out.