I've generally had buffer-cache hit rates in the 99.9% range, which ends up being minimal read I/O. (This is on AWS Aurora, where these bo disk cache and so sha

I've generally had buffer-cache hit rates in the 99.9% range, which ends up being minimal read I/O. (This is on AWS Aurora, where these bo disk cache and so shared_buffers is the primary cache, but an equivalent measure for vanilla postgres exists.) In those scenarios,there's very little read I/O. CPU is the primary bottleneck. That's why we run up as many as 10 Aurora readers (autoscaled with traffic).