Foreword

Reliability is a conversation.

It is a conversation we have with our infrastructure, our systems, and our services as we attempt to operate them. It is a conversation we have with complexity, security, scalability, and velocity in the hopes they will emerge in the way we need them. It is a conversation we have with ethics, privacy, and justice as we attempt to do the right thing for the people who depend on us. And finally, it is a conversation we have with our colleagues so we can work together to build what matters to us.

If there is anything the world needs right now (either the now of this writing or the now when you are reading this), it is better conversations. They are not easy. We can use all of the help we can get with them.

And that’s where SLIs and SLOs come into the picture. For me, they offer a tool, a practice, a model—whatever you want to call it—for having better reliability conversations. Conversations that put the humans first. SLIs and SLOs help us think about, communicate, and interact with reliability in a new way. They aren’t actors’ scripts for some David Mamet-esque play telling us exactly what to say—where to speak or where to put the pauses. I’m pretty sure we wouldn’t want them if they were.

Instead, SLIs and SLOs give us a little guidance when we need it. “Hmm, your customer’s latency might be a bit better if you zigged there instead of zagging” or “Are you sure you want to deploy a new version now?” or “Oh, so that’s what is important to our users; maybe we’d better start paying attention to that...” And given all of the different conversations mentioned earlier that we are responsible for navigating, this guidance is gold.

If we were to play the old good news/bad news game, the bad news is just as conversations about reliability can be hard at times, conversations about conversations about reliability can be less straightforward than we’d like. SLIs and SLOs in theory are potentially easy, but in practice, not always so much.

The other piece of soggy news is that just as reliability conversations (at least the good ones) never really end, so too it is with SLIs and SLOs. They don’t finish. As Rilke said: “Live the questions now.”

The good (albeit slightly less poetic) news is that you have this book. Alex and the other contributors have already lived some of the questions, and they are ready to share what they’ve learned with you. This can help you mine the gold and get the most from what SLIs and SLOs have to offer.

I don’t want to keep you any longer from reading the rest of this book, but I will use up the free “Dear reader” card you get when you agree to write a book foreword:

Dear reader, please use all of the advice in this book (and any other tool you encounter) to have better conversations. I’m counting on you.

David N. Blank-Edelman

Curator/Editor of Seeking SRE

and Cofounder of SREcon