In the doc in github https://github.com/neondatabase/neon/blob/main/docs/walservice.md:
That's different from how streaming replication usually works,
where the replica initiates the connection. To do that,
there is a component called the "WAL proposer".
WAL proposer is it embedded in postgresql or is it a separate process?
Are there any advantages to this design if there are multiple instances of PostgreSQL on a single machine?