We always build systems hoping they never need any maintenance. The truth is, they often do. Especially when there are changes happening. I once took a week of

We always build systems hoping they never need any maintenance. The truth is, they often do. Especially when there are changes happening. I once took a week off and we went down on day 2. Other times, I'm convinced I could've gone 6 months without anything breaking. At Twitter's scale, I'm sure there are systems where everything is automated and self-healing. But there are probably other systems that are more fragile. And then there's the eternal race against scale; eventually a system with no maintenance will get buried under the weight of its own data or the scope of its usage. That always requires some work.