diff --git a/src/services/query_service.cpp b/src/services/query_service.cpp
index 845aad71..b3a01db9 100644
--- a/src/services/query_service.cpp
+++ b/src/services/query_service.cpp
@@ -57,12 +57,37 @@ void query_service::work()
     if (!started(bind(router, query_dealer, notify_dealer)))
         return;
 
+    zmq::poller poller;
+    poller.add(router);
+    poller.add(query_dealer);
+    poller.add(notify_dealer);
+
     // TODO: tap in to failure conditions, such as high water.
-    // Relay messages between router and dealer (blocks on context).
-    //*************************************************************************
-    // TODO: integrate notify_dealer into relay.
-    relay(router, query_dealer);
-    //*************************************************************************
+    while (!poller.terminated() && !stopped())
+    {
+        const auto signaled = poller.wait();
+
+        if (signaled.contains(router.id()) &&
+            !forward(router, query_dealer))
+        {
+            log::warning(LOG_SERVER)
+                << "Failed to forward from router to query_dealer.";
+        }
+
+        if (signaled.contains(query_dealer.id()) &&
+            !forward(query_dealer, router))
+        {
+            log::warning(LOG_SERVER)
+                << "Failed to forward from query_dealer to router.";
+        }
+
+        if (signaled.contains(notify_dealer.id()) &&
+            !forward(notify_dealer, router))
+        {
+            log::warning(LOG_SERVER)
+                << "Failed to forward from notify_dealer to router.";
+        }
+    }
 
     // Unbind the sockets and exit this thread.
     finished(unbind(router, query_dealer, notify_dealer));
diff --git a/src/workers/notification_worker.cpp b/src/workers/notification_worker.cpp
index c729a10e..2c88a5a1 100644
--- a/src/workers/notification_worker.cpp
+++ b/src/workers/notification_worker.cpp
@@ -138,6 +138,7 @@ void notification_worker::work()
     // Other threads connect and disconnect dynamically to send updates.
     while (!poller.terminated() && !stopped())
     {
+        // BUGBUG: this can fail on some platforms if interval is > 1000.
         poller.wait(interval);
         purge();
     }