Cloudflare built a global cache purge system that runs under 150 ms.

This is how they did it.

Using RockDB to maintain local CDN cache, and a peer-to-peer data center distributed system and clever engineering, they went from 1.5 second purge, down to 150 ms.

However, this isn’t full picture, because that 150 ms is just actually the P50. In this video I explore Clouldflare CDN work, how the old core-based centralized quicksilver, lazy purge work compared to the new coreless, decentralized active purge. In it I explore the pros and cons of both systems and give you my thoughts of this system.

0:00 Intro

4:25　From Core Base Lazy Purge to Coreless Active

12:50 CDN Basics

16:00 TTL Freshness

17:50 Purge

20:00 Core-Based Purge

24:00 Flexible Purges

26:36 Lazy Purge

30:00 Old Purge System Limitations

36:00 Coreless / Active Purge

39:00 LSM vs BTree

45:30 LSM Performance issues

48:00 How Active Purge Works

50:30 My thoughts about the new system

58:30 Summary

Cloudflare blog

https://blog.cloudflare.com/instant-purge/

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