97 Things Every SRE Should Know

Chapter 28. I Have an Error Budget—Now What?

Alex Hidalgo

Nobl9

SLIs, SLOs, and error budgets are the bedrock of site reliability engineering. Much has been written about what they are, but not much has been written about how to use them. The classic example of, “Ship features when you have an error budget; halt releases and focus on reliability when you don’t,” is a bit archaic and doesn’t really expose all of the great decisions you can make with your data.

So if it’s not just about shipping features or not, what can we use error budget data for?

Well, I would be remiss if I didn’t mention that you can, in fact, use error budgets to determine when to release new features. Changes to code or configuration are the single most common vector of new problems, so sometimes it actually is completely reasonable to say, “Let’s slow down a little bit and figure out how to make things more stable.” But let’s spend some time talking about what other decisions you can make, using error budget data.

A more reasonable use of error budget data is to determine the focus of your project work. SLO-based approaches to reliability are about providing you with better data to have better discussions and make better decisions. Having a hard mandate about when to ship code probably doesn’t make much sense in many situations, but using this data to help you figure out what your team should be focused ...