GitHub, autoscaling, and the component substitution fallacy

The GitHub outage was partly caused by an autoscaling policy that tracked only the host service’s load, ignoring the Istio sidecar’s concurrency limits, so the sidecar pod saturated and failed to scale. The author warns that fixing such mis-configurations addresses a single defect, but reliability requires recognizing many latent component flaws—a concept he calls the component substitution fallacy.