[mattashii]

Some parts of the PostgreSQL start-up sequence take a long time:

- Initializing shared memory -> We, for now, have only small instances, so that doesn't hit us as hard

- Reading data directories -> We don't have to do that at all

- Replaying WAL from a previous unclean shutdown -> We don't need to do that, PageServer is responsible for that

- When initializing a whole new database: Initializing the data directory -> We have a copy that each instance gets initialized from, which makes the process "copy those ~16MB in the background", which saves us from having to do the costly initialization process.

And there's several more infrastructural optimizations, such as pre-loading the docker images onto the hosts.