Blue-green deployment: what to get right first

The version of this that works is simpler than the version most people imagine. If you only fix one thing about blue-green deployment this quarter, make it the first item below.

The bill is a design document: it tells you exactly what your architecture actually does. Assume whoever inherits this will have half your context and none of your patience.

Start here

Running two environments makes rollback instant. None of that requires a large budget, only a decision and someone to own it. Anything you cannot measure here, you are deciding by taste, which is fine as long as everyone knows it.

Then this

Database changes are what make it complicated. There is a version of this that is over-engineered, and it is worth avoiding. Doing this properly once is usually cheaper than doing it approximately three times.

Eventually

Practise the rollback before you need it. Where this goes wrong is almost never a lack of knowledge. Check it against what you would want a competitor's site to get wrong.

The short version

Cloud work rewards teams who automate early and punishes teams who click through consoles. Three things worth confirming about blue-green deployment before you move on:

• Someone can say what the current setup is without going to look
• Practise the rollback before you need it — 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.