Currently, the PrometheusRemoteStorageFailures and PrometheusRemoteWriteBehind alerts are critical. However, especially with remote-write setups, many users will run HA pairs (or groups) of Prometheus servers, and the remote-write receiver will have some way of dedup'ing the incoming samples. If that's the case, just one Prometheus replica having trouble with remote-write should just be a warning. The alert should be critical only if all members of the HA group have trouble.