diff --git a/base-kv/base-kv-store-client/src/main/java/org/apache/bifromq/basekv/client/BaseKVStoreClient.java b/base-kv/base-kv-store-client/src/main/java/org/apache/bifromq/basekv/client/BaseKVStoreClient.java
index 2333a3e10..a42016200 100644
--- a/base-kv/base-kv-store-client/src/main/java/org/apache/bifromq/basekv/client/BaseKVStoreClient.java
+++ b/base-kv/base-kv-store-client/src/main/java/org/apache/bifromq/basekv/client/BaseKVStoreClient.java
@@ -126,7 +126,7 @@ final class BaseKVStoreClient implements IBaseKVStoreClient {
     // key: storeId
     private final Map<String, List<IQueryPipeline>> lnrQueryPplns = Maps.newHashMap();
     private final AtomicReference<NavigableMap<Boundary, KVRangeSetting>> effectiveRouter =
-        new AtomicReference<>(new TreeMap<>(BoundaryUtil::compare));
+        new AtomicReference<>(Collections.unmodifiableNavigableMap(new TreeMap<>(BoundaryUtil::compare)));
 
     // key: serverId, val: storeId
     private volatile Map<String, String> serverToStoreMap = Maps.newHashMap();
@@ -486,7 +486,7 @@ private boolean refreshRangeRoute(ClusterInfo clusterInfo) {
         }
         NavigableMap<Boundary, KVRangeSetting> last = effectiveRouter.get();
         if (!router.equals(last)) {
-            effectiveRouter.set(router);
+            effectiveRouter.set(Collections.unmodifiableNavigableMap(router));
             return true;
         }
         return false;
@@ -519,7 +519,7 @@ private void patchRouter(String leaderStoreId, KVRangeDescriptor latest) {
                 }
             }
             patched.put(setting.boundary, setting);
-            effectiveRouter.compareAndSet(router, patched);
+            effectiveRouter.compareAndSet(router, Collections.unmodifiableNavigableMap(patched));
         }
     }
 
diff --git a/bifromq-inbox/bifromq-inbox-store/src/main/java/org/apache/bifromq/inbox/store/InboxStoreGCProcessor.java b/bifromq-inbox/bifromq-inbox-store/src/main/java/org/apache/bifromq/inbox/store/InboxStoreGCProcessor.java
index 39b676283..fb206d974 100644
--- a/bifromq-inbox/bifromq-inbox-store/src/main/java/org/apache/bifromq/inbox/store/InboxStoreGCProcessor.java
+++ b/bifromq-inbox/bifromq-inbox-store/src/main/java/org/apache/bifromq/inbox/store/InboxStoreGCProcessor.java
@@ -14,7 +14,7 @@
  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  * KIND, either express or implied.  See the License for the
  * specific language governing permissions and limitations
- * under the License.    
+ * under the License.
  */
 
 package org.apache.bifromq.inbox.store;
@@ -22,6 +22,10 @@
 import static org.apache.bifromq.basekv.client.KVRangeRouterUtil.findByBoundary;
 import static org.apache.bifromq.basekv.utils.BoundaryUtil.FULL_BOUNDARY;
 
+import com.google.common.collect.Sets;
+import java.util.Collection;
+import java.util.concurrent.CompletableFuture;
+import lombok.extern.slf4j.Slf4j;
 import org.apache.bifromq.basekv.client.IBaseKVStoreClient;
 import org.apache.bifromq.basekv.client.KVRangeSetting;
 import org.apache.bifromq.basekv.client.exception.BadRequestException;
@@ -33,9 +37,6 @@
 import org.apache.bifromq.inbox.storage.proto.GCReply;
 import org.apache.bifromq.inbox.storage.proto.GCRequest;
 import org.apache.bifromq.inbox.storage.proto.InboxServiceROCoProcInput;
-import java.util.Collection;
-import java.util.concurrent.CompletableFuture;
-import lombok.extern.slf4j.Slf4j;
 
 @Slf4j
 public class InboxStoreGCProcessor implements IInboxStoreGCProcessor {
@@ -49,8 +50,8 @@ public InboxStoreGCProcessor(IBaseKVStoreClient storeClient, String localStoreId
 
     @Override
     public final CompletableFuture<Result> gc(long reqId, long now) {
-        Collection<KVRangeSetting> rangeSettingList = findByBoundary(FULL_BOUNDARY,
-            storeClient.latestEffectiveRouter());
+        Collection<KVRangeSetting> rangeSettingList = Sets.newHashSet(findByBoundary(FULL_BOUNDARY,
+            storeClient.latestEffectiveRouter()));
         if (localServerId != null) {
             rangeSettingList.removeIf(rangeSetting -> !rangeSetting.leader.equals(localServerId));
         }