Company

Cloudflare

Every Cloudflare engineering case study on TechLogStack — real production incidents, post-mortems, and fixes.

Cloudflare Reliability
18 min

Cloudflare Fixed a React Security Vulnerability and Broke the Entire Network

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.

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Cloudflare Reliability
16 min

Cloudflare's Datacenter Partner Failed and the Control Plane Went Dark for 40 Hours

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.

~40 hours control plane down
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Cloudflare Reliability
17 min

A Database Permission Change in ClickHouse Took Down 28% of Cloudflare's HTTP Traffic

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.

28% HTTP traffic impacted 6 hours total duration 2.5h to find root cause
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