> However, if multiple synchronous standby replicas are configured, then this means that stale reads are possible, since Postgres by default does not necessaril

> However, if multiple synchronous standby replicas are configured, then this means that stale reads are possible, since Postgres by default does not necessarily wait for all replicas to ack the write. It depends on the replication configuration and where reads are directed. It seems synchronous replication still refers to durability of a commit. Once it‘s stored on the replica persistently it doesn‘t block anymore, so no strict serializability. Macdice‘s comment and the link hold lots of info on this.