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Every Cloudflare engineering case study on TechLogStack — real production incidents, post-mortems, and fixes.
In late 2025, Cloudflare was rolling out a fix for a React security vulnerability. To do so, they needed to disable an internal testing tool with a global killswitch. The killswitch, unexpectedly, triggered a bug that sent HTTP 500 errors across Cloudflare's entire global network. This was the third major configuration-related global outage in two years.
A ClickHouse permission update caused the bot detection file to triple in size. Cloudflare's proxies were not designed to survive that — and for six hours, neither was most of the internet.
A well-reviewed security patch hit production traffic patterns it had never seen in testing, and a retry amplification loop did the rest.
On November 2, 2023, Cloudflare's primary datacenter partner experienced a power failure. The control plane — the system that lets customers configure DNS, firewall rules, and every Cloudflare service — went dark. It stayed dark, in various forms, for nearly 40 hours. The postmortem introduced a concept Cloudflare hadn't had before: Code Orange.
On November 2, 2023 — the same day as the control plane datacenter failure — Cloudflare also experienced a separate six-hour global outage. The cause: a database permission change in ClickHouse generated a corrupt configuration file that was silently propagated to every server in Cloudflare's Bot Management system, crashing it globally.