ok, it works, but how?

To sync Postgres nodes, PgRocks sits on a shared RocksDB database. This share must be set up in some known way e.g. by using RocksDB-cloud, Rocksplicator, Parity-like blockchain, async server, etc. One may select the bottom layer implementation that satisfies their demands. Whatever the choice is, PgRocks will do the job seamlessly.