Comment by vvpan

Sometime in 2017/18 it has been found that one of the biggest bottlenecks for the network were propagation speeds and that those were largely weighed down by disk writes. Thus pretty much the whole network switched to SSDs and things improved tremendously. Some other networks have implemented stateless clients and Ethereum has been working on going in that direction for a while with a lot of effort being dedicated to it this year specifically.