We halved DNS build delay and cut memory use by 85%

Cloudflare optimized its DNS propagation pipeline by implementing a targeted build planner that only rebuilds the specific zone settings that changed, rather than rebuilding entire zones. This optimization reduced peak memory usage by 85% and cut DNS change propagation time in half, while handling nearly three times the event volume since 2022. The key challenge was safely determining the minimal amount of work needed for each change to avoid stale or incorrect DNS data at the edge.