I've been looking at wasm some. its totally unclear to me how this would support Postgres - which requires a posix filesystem interface, and the ability to fork children that operate on a shared memory segment. Were these facilities added to a wasp runtime, or was there major surgery on the Postgres codebase. I feel like I must be missing a simple answer.

All of Linux is in there, too, I think. Postgres-on-Linux-in-WASM