![[wl_client_libpqwalreceiverreceive.png|256]] - **Description**: The WAL receiver process on a standby server is waiting to receive a chunk of transaction data from the remote primary. Technically, this process is blocked on a network socket read (`recv()` or `poll()`) waiting for the TCP stream of WAL records to arrive, which indicates either an idle primary or network congestion. - **Resources**: [[Network]], [[CPU]]