Cloudflare's 150ms global cache purge | Deep Dive

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

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Stay Awesome,
Hussein

[BR-lxpy]

Agreed that the old version of purge was perplexing. Why did it take 1500ms to send a message to all the datacenters that a certain URL should be on the purge list? And was every single request checked against that purge list instead of being removed from the cache? That seems extremely wasteful. Also doesn't make sense that the simplest case of purge, the URL purge is 240ms, while a prefix or tag based one is 150?

[singha]

Nice video! I recently became interested in cloudflare’s offering.

I came across their Hyperdrive product which aims to make SQL queries faster by distributing a single region database globally using cache, similar to prisma accelerate.

Would it be possible for a deep dive video and benchmarking the improvement in terms of latency? Some of us want to see if this is a viable solution as an alternative to read replicas.

Thank you for your work!

[nexovec]

We have CDN77 here and those guys have some pretty insane tech, they do craazy stuff with recoding video. It's nice seeing good technology used where it's actually supposed to for once. No it's not related to the video sorry.

[bgroesser]

Listening to this, i found out that i have to pronounce my s as sh.
Not sure where that bit of knowledge came from but no, we dont pronounce Australia as 'Aushtralia'. Not saying we dont do weird things, but this is new to me.

[AmmaarSolkar]

Do we know what queue system do they use? how do you look through the contents of a queue fast enough that you can afford to do it before every request?

[monireol]

What a surprise.
I am just exploring exactly cloudflare cdn

[monireol]

I was watching your old video.
Why not to shard database