Specifically on the cost of forking a process for each connection (vs using threads), there are active efforts to make Postgres multi-threaded.

Since Postgres is a mature project, this is a non-trivial effort. See the Postgres wiki for some context: https://wiki.postgresql.org/wiki/Multithreading

But, I'm hopeful that in 2-3 years from now, we'll see this bear fruition. The recent asynchronous read I/O improvements in Postgres 18 show that Postgres can evolve, one just needs to be patient, potentially help contribute, and find workarounds (connection pooling, in this case).

Would be nice if the OrioleDB improvements were to be incorporated in postgresql proper some day.. https://www.slideshare.net/slideshow/solving-postgresql-wick...