Varnish is a high-performance open source HTTP accelerator. Norway's largest online newspaper Verdens Gang (http://www.vg.no) used 3 Varnish to replace the original 12 squids, and the performance is actually better than before.
Varnish author Poul-Henning Kamp, one of the FreeBSD kernel developers, believes that computers today are much more complex than they were in 1975. In 1975, there were only two storage media: RAM and hard drives. However, in addition to the main memory, the memory of the computer system now includes L1, L2, and even L3 cache in the CPU. The hard disk also has its own cache device, so it is impossible for the structure of squid cache to handle object replacement by itself to know these conditions and optimize them, but the operating system can know these conditions, so this part of the work should be handed over to the operation. System processing, this is the Varnish cache design architecture.
Official: https://www.varnish-cache.org/