Improving Cloudflare’s products and services, one feature request at a time

This post details the development and implementation of a new feature called 'Secondary DNS Override'. This feature allows Cloudflare to act as a Secondary DNS provider and, in specific cases, respond to DNS queries with Cloudflare's own IP space, thereby enabling HTTP proxy services (Layer 7 DDoS mitigation, WAF, CDN). This was developed in response to customer feedback from a large financial institution (Customer A) and another organization (Customer B) who wanted to leverage Cloudflare's proxy services while using Cloudflare as a Secondary DNS provider. The feature was initially released via API in November 2019, with UI parity following in the subsequent quarter.