How the Dyn outage affected Cloudflare

This post details Cloudflare's response to the Dyn DDoS outage, focusing on improvements to its internal DNS infrastructure. The key technical contributions include: 1. Analysis of DNS error rates across data centers during the Dyn outage to understand the impact of third-party DNS provider unavailability. 2. Identification of the need for 'serve stale while revalidating' for DNS records to mitigate the effects of upstream DNS outages. 3. Implementation and rollout of this 'serve stale while revalidating' strategy to improve resilience for customers using CNAME'd DNS records that rely on third-party DNS providers.