Switched on caching for the networked filesystems (EFS/NFS) that I use, so they are now backed by a local block device. It isn't any faster, but it feels better knowing that it's cached...

Essentially added the ,fsc mount option, installed the cachefilesd package, uncommented the RUN=yes line in /etc/default/cachefilesd. The directory /var/cache/fscache is filling up, so it's doing something.

One thing that is slow over EFS (NFS) is restarting an Elixir or Nodejs server (running them is fine). These access many files, so the network latency adds up. With a cache, this is still the same; it needs to check whether the files are changed after all. Running PHP applications from a networked filesystem is actually very fast, despite what the internet says; opcache does its thing rather well.