Wikipedia now has up to 1000X reduction of ATS disk read latency at the p999

Probably Apache Traffic Server

Apache Traffic Server:

Here’s how they use it along with Varnish:

Having a 2nd level cache that only has a 2% cache hit rate doesn't really seem worth it...

Isn't it better to just get rid of that layer all together and have a simpler system?

It defines that term at the top of the article