What’s the most surprising AWS dependency that took down your app?

Hey everyone, Serkan here.

While building the AWS risk analysis engine for Uptime.cx, I’ve been diving deep into how modern cloud architectures actually fail in the real world.

The biggest takeaway? It’s almost never a sophisticated cyber attack or a complex zero-day. It’s usually a single, forgotten misconfiguration—like a rogue Security Group, an expired certificate, or a single Redis node taking down a "highly available" multi-AZ setup because of a hidden dependency.

I'm curious about your "war stories". What’s the dumbest or most surprising hidden single point of failure that caused an outage for your team? And more importantly, how long did it take you to find the root cause during the panic?