diff --git a/server/internal/biz/node.go b/server/internal/biz/node.go
index 32027722..536279d6 100644
--- a/server/internal/biz/node.go
+++ b/server/internal/biz/node.go
@@ -51,6 +51,7 @@ type NodeRepo interface {
 	GetNode(context.Context, string) (*Node, error)
 	ListAllDevices(context.Context) ([]*DeviceInfo, error)
 	FindDeviceByAliasId(string) (*DeviceInfo, error)
+	Ready() bool
 }
 
 type NodeUsecase struct {
@@ -77,3 +78,7 @@ func (uc *NodeUsecase) ListAllDevices(ctx context.Context) ([]*DeviceInfo, error
 func (uc *NodeUsecase) FindDeviceByAliasId(aliasId string) (*DeviceInfo, error) {
 	return uc.repo.FindDeviceByAliasId(aliasId)
 }
+
+func (uc *NodeUsecase) Ready() bool {
+	return uc.repo.Ready()
+}
diff --git a/server/internal/biz/pod.go b/server/internal/biz/pod.go
index 4162db75..98da6d4c 100644
--- a/server/internal/biz/pod.go
+++ b/server/internal/biz/pod.go
@@ -37,6 +37,7 @@ type PodInfo struct {
 type PodRepo interface {
 	ListAll(context.Context) ([]*Container, error)
 	FindOne(context.Context, string, string) (*Container, error)
+	Ready() bool
 }
 
 type PodUseCase struct {
@@ -72,6 +73,10 @@ func (uc *PodUseCase) ListAll(ctx context.Context) ([]*Container, error) {
 	return uc.repo.ListAll(ctx)
 }
 
+func (uc *PodUseCase) Ready() bool {
+	return uc.repo.Ready()
+}
+
 func ContainersStatisticsInfo(containers []*Container, deviceId string) (int32, int32, int32) {
 	var vGPU int32 = 0
 	var core int32 = 0
diff --git a/server/internal/data/node.go b/server/internal/data/node.go
index 4f59ab6e..a9537176 100644
--- a/server/internal/data/node.go
+++ b/server/internal/data/node.go
@@ -30,6 +30,7 @@ type nodeRepo struct {
 	log        *log.Helper
 	mutex      sync.RWMutex
 	providers  []provider.Provider
+	ready      bool
 }
 
 // NewNodeRepo .
@@ -100,6 +101,16 @@ func (r *nodeRepo) updateLocalNodes() {
 		}
 		r.mutex.Lock()
 		r.nodes = n
+		if !r.ready {
+			r.ready = true
+			r.log.Infof("node data initialized: %d nodes, %d devices", len(n), func() int {
+				count := 0
+				for _, node := range n {
+					count += len(node.Devices)
+				}
+				return count
+			}())
+		}
 		r.mutex.Unlock()
 	}
 }
@@ -116,7 +127,26 @@ func (r *nodeRepo) init() {
 	})
 	stopCh := make(chan struct{})
 	informerFactory.Start(stopCh)
-	informerFactory.WaitForCacheSync(stopCh)
+	synced := informerFactory.WaitForCacheSync(stopCh)
+	syncedOK := true
+	for _, ok := range synced {
+		if !ok {
+			syncedOK = false
+			break
+		}
+	}
+	if syncedOK {
+		r.log.Info("node informer synced successfully")
+	} else {
+		r.log.Warn("node informer failed to sync, data may be incomplete")
+	}
+}
+
+// Ready returns true if the node informer has successfully synced and populated data.
+func (r *nodeRepo) Ready() bool {
+	r.mutex.RLock()
+	defer r.mutex.RUnlock()
+	return r.ready
 }
 
 func (r *nodeRepo) onAddNode(obj interface{}) {
diff --git a/server/internal/data/pod.go b/server/internal/data/pod.go
index e17857ec..6fa7f30b 100644
--- a/server/internal/data/pod.go
+++ b/server/internal/data/pod.go
@@ -24,6 +24,7 @@ type podRepo struct {
 	pods      map[k8stypes.UID]*biz.PodInfo
 	mutex     sync.RWMutex
 	log       *log.Helper
+	ready     bool
 }
 
 func NewPodRepo(data *Data, logger log.Logger) biz.PodRepo {
@@ -47,7 +48,29 @@ func (r *podRepo) init() {
 	})
 	stopCh := make(chan struct{})
 	informerFactory.Start(stopCh)
-	informerFactory.WaitForCacheSync(stopCh)
+	synced := informerFactory.WaitForCacheSync(stopCh)
+	syncedOK := true
+	for _, ok := range synced {
+		if !ok {
+			syncedOK = false
+			break
+		}
+	}
+	if syncedOK {
+		r.mutex.Lock()
+		r.ready = true
+		r.mutex.Unlock()
+		r.log.Info("pod informer synced successfully")
+	} else {
+		r.log.Warn("pod informer failed to sync, data may be incomplete")
+	}
+}
+
+// Ready returns true if the pod informer has successfully synced.
+func (r *podRepo) Ready() bool {
+	r.mutex.RLock()
+	defer r.mutex.RUnlock()
+	return r.ready
 }
 
 func (r *podRepo) onAddPod(obj interface{}) {
diff --git a/server/internal/server/http.go b/server/internal/server/http.go
index 73906944..213417b0 100644
--- a/server/internal/server/http.go
+++ b/server/internal/server/http.go
@@ -57,10 +57,13 @@ func NewHTTPServer(c *conf.Bootstrap,
 	srv.HandlePrefix("/q/", openapiv2.NewHandler())
 	srv.Handle("/metrics", promhttp.Handler())
 	srv.HandleFunc("/readyz", func(w http.ResponseWriter, r *http.Request) {
-		// Reaching this handler means the server is listening and the informer
-		// caches have already synced (the backend only starts serving after that).
-		w.WriteHeader(nethttp.StatusOK)
-		_, _ = w.Write([]byte("ok"))
+		if node.Ready() {
+			w.WriteHeader(nethttp.StatusOK)
+			_, _ = w.Write([]byte("ok"))
+		} else {
+			w.WriteHeader(nethttp.StatusServiceUnavailable)
+			_, _ = w.Write([]byte("not ready"))
+		}
 	})
 	return srv
 }
diff --git a/server/internal/service/card.go b/server/internal/service/card.go
index 4d3ec2b4..044e327c 100644
--- a/server/internal/service/card.go
+++ b/server/internal/service/card.go
@@ -21,7 +21,13 @@ func NewCardService(node *biz.NodeUsecase, pod *biz.PodUseCase, ms *MonitorServi
 }
 
 func (s *CardService) GetAllGPUs(ctx context.Context, req *pb.GetAllGpusReq) (*pb.GPUsReply, error) {
-	filters := req.Filters
+	var filters *pb.GetAllGpusReq_Filters
+	if req != nil {
+		filters = req.Filters
+	}
+	if filters == nil {
+		filters = &pb.GetAllGpusReq_Filters{}
+	}
 	deviceInfos, err := s.node.ListAllDevices(ctx)
 	if err != nil {
 		return nil, err
@@ -115,7 +121,13 @@ func (s *CardService) GetAllGPUTypes(ctx context.Context, req *pb.GetAllGpusReq)
 	var res = &pb.GPUsReply{List: []*pb.GPUReply{}}
 	seenTypes := make(map[string]struct{})
 
-	filters := req.Filters
+	var filters *pb.GetAllGpusReq_Filters
+	if req != nil {
+		filters = req.Filters
+	}
+	if filters == nil {
+		filters = &pb.GetAllGpusReq_Filters{}
+	}
 	provider := strings.Trim(filters.Provider, " ")
 	for _, device := range deviceInfos {
 		if provider != "" && provider != device.Provider {
@@ -134,6 +146,9 @@ func (s *CardService) GetAllGPUTypes(ctx context.Context, req *pb.GetAllGpusReq)
 }
 
 func (s *CardService) GetGPU(ctx context.Context, req *pb.GetGpuReq) (*pb.GPUReply, error) {
+	if req == nil {
+		return &pb.GPUReply{}, nil
+	}
 	devices, err := s.node.ListAllDevices(ctx)
 	if err != nil {
 		return nil, err
diff --git a/server/internal/service/container.go b/server/internal/service/container.go
index c108586d..91872b0d 100644
--- a/server/internal/service/container.go
+++ b/server/internal/service/container.go
@@ -45,7 +45,13 @@ func uniqueNonEmpty(values []string) []string {
 }
 
 func (s *ContainerService) GetAllContainers(ctx context.Context, req *pb.GetAllContainersReq) (*pb.ContainersReply, error) {
-	filters := req.Filters
+	var filters *pb.GetAllContainersReq_Filters
+	if req != nil {
+		filters = req.Filters
+	}
+	if filters == nil {
+		filters = &pb.GetAllContainersReq_Filters{}
+	}
 	containers, err := s.pod.ListAllContainers(ctx)
 	if err != nil {
 		return nil, err
diff --git a/server/internal/service/node.go b/server/internal/service/node.go
index 37b43d1c..5f1e954a 100644
--- a/server/internal/service/node.go
+++ b/server/internal/service/node.go
@@ -26,16 +26,33 @@ func NewNodeService(uc *biz.NodeUsecase, pod *biz.PodUseCase, summary *biz.Summa
 	return &NodeService{uc: uc, pod: pod, summary: summary, ms: ms}
 }
 
+// Ready returns true if both node and pod informers have synced.
+func (s *NodeService) Ready() bool {
+	return s.uc.Ready() && s.pod.Ready()
+}
+
 func (s *NodeService) GetSummary(ctx context.Context, req *pb.GetSummaryReq) (*pb.DeviceSummaryReply, error) {
-	filters := req.Filters
+	var filters *pb.GetSummaryReq_Filters
+	if req != nil {
+		filters = req.Filters
+	}
 	var res = &pb.DeviceSummaryReply{}
+	if filters == nil {
+		filters = &pb.GetSummaryReq_Filters{}
+	}
 	t, err := s.summary.GetGPUSummary(ctx, filters.DeviceId, filters.NodeUid, filters.Type)
 	copier.Copy(&res, &t)
 	return res, err
 }
 
 func (s *NodeService) GetAllNodes(ctx context.Context, req *pb.GetAllNodesReq) (*pb.NodesReply, error) {
-	filters := req.Filters
+	var filters *pb.GetAllNodesReq_Filters
+	if req != nil {
+		filters = req.Filters
+	}
+	if filters == nil {
+		filters = &pb.GetAllNodesReq_Filters{}
+	}
 	nodes, err := s.uc.ListAllNodes(ctx)
 	if err != nil {
 		return nil, err
@@ -88,6 +105,9 @@ func (s *NodeService) GetAllNodes(ctx context.Context, req *pb.GetAllNodesReq) (
 }
 
 func (s *NodeService) GetNode(ctx context.Context, req *pb.GetNodeReq) (*pb.NodeReply, error) {
+	if req == nil || req.Uid == "" {
+		return &pb.NodeReply{}, nil
+	}
 	node, err := s.uc.GetNode(ctx, req.Uid)
 	if err != nil {
 		return nil, err