Blue-green deployment: the questions we get asked most

The version of this that works is simpler than the version most people imagine. The questions about blue-green deployment that come up most often on our calls.

Operability is a feature, and it has to be built rather than bought. Anything you cannot measure here, you are deciding by taste, which is fine as long as everyone knows it.

Do we need to care about this?

Running two environments makes rollback instant. Where this goes wrong is almost never a lack of knowledge. It is the sort of thing that looks like polish right up until it costs you an enquiry.

Can it wait until after launch?

Occasionally. More often the post-launch version costs several times the pre-launch one. This is the sort of thing that compounds, quietly, in both directions.

How do we know it is working?

Practise the rollback before you need it. There is a version of this that is over-engineered, and it is worth avoiding. The teams that stay on top of it are the ones who put it on a calendar rather than a wish list.

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
• Database changes are what make it complicated — 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.