This past Saturday, 19 July, marked the one-year anniversary of the CrowdStrike incident. Eight million Windows machines blue-screened across airports, hospitals, and a variety of other businesses.

(It took two issues of Complex Machinery to cover it all – "Blue Screen for Armageddon" and "Embers and Ashes" – the first of which was lucky number 013.)

This event held lessons about risk, complexity, and our world's connectedness.

The key lesson of complexity and risk – and part of why I find those subjects so interesting – is that these incidents rarely have a single, simple root cause.

Instead, several smaller issues collide in an unfortunate manner. To pull a line from newsletter 013:

That's because the entire complex system is the cause. All of those moving parts are why Things Happen and also why Things Eventually Fall Apart. Complexity is its own worst enemy, appearing to function yet always a step away from a breakdown.

CrowdStrike may have been the most recent such incident ... but there will be others.

We are surrounded by complex systems. They appear to hum along smoothly, providing an illusion of stability, but they are continually one bad day away from a collapse.

I'll cap off with my favorite explanation of complex systems, from an O'Reilly Radar piece I wrote a couple years back:

What makes a complex system troublesome isn’t the sheer number of connections. It’s not even that many of those connections are invisible because a person can’t see the entire system at once. The problem is that those hidden connections only become visible during a malfunction: a failure in Component B affects not only neighboring Components A and C, but also triggers disruptions in T and R. R’s issue is small on its own, but it has just led to an outsized impact in Φ and Σ.

(And if you just asked “wait, how did Greek letters get mixed up in this?” then … you get the point.)