diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/store/impl/MemoryFederationStateStore.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/store/impl/MemoryFederationStateStore.java
new file mode 100644
index 00000000000..7fdc4a91ea8
--- /dev/null
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/store/impl/MemoryFederationStateStore.java
@@ -0,0 +1,138 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership.  The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "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.
+ */
+
+package org.apache.hadoop.yarn.server.federation.store.impl;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+import org.apache.hadoop.yarn.exceptions.YarnException;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterId;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterInfo;
+import org.apache.hadoop.yarn.server.federation.store.FederationMembershipStateStore;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterDeregisterRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterDeregisterResponse;
+import org.apache.hadoop.yarn.server.federation.store.records.GetSubClusterInfoRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.GetSubClusterInfoResponse;
+import org.apache.hadoop.yarn.server.federation.store.records.GetSubClustersInfoRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.GetSubClustersInfoResponse;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterHeartbeatRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterHeartbeatResponse;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterRegisterRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterRegisterResponse;
+import org.apache.hadoop.yarn.server.records.Version;
+import org.apache.hadoop.yarn.util.MonotonicClock;
+
+import com.google.common.annotations.VisibleForTesting;
+
+/**
+ * In-memory implementation of FederationMembershipStateStore.
+ */
+public class MemoryFederationStateStore
+    implements FederationMembershipStateStore {
+
+  private final Map<SubClusterId, SubClusterInfo> membership =
+      new ConcurrentHashMap<SubClusterId, SubClusterInfo>();
+  private final MonotonicClock clock = new MonotonicClock();
+
+  @Override
+  public Version getMembershipStateStoreVersion() {
+    return null;
+  }
+
+  @Override
+  public SubClusterRegisterResponse registerSubCluster(
+      SubClusterRegisterRequest request) throws YarnException {
+    SubClusterInfo subClusterInfo = request.getSubClusterInfo();
+    subClusterInfo.setLastStartTime(clock.getTime());
+    membership.put(subClusterInfo.getSubClusterId(), subClusterInfo);
+    return SubClusterRegisterResponse.newInstance();
+  }
+
+  @Override
+  public SubClusterDeregisterResponse deregisterSubCluster(
+      SubClusterDeregisterRequest request) throws YarnException {
+    SubClusterInfo subClusterInfo = membership.get(request.getSubClusterId());
+    if (subClusterInfo == null) {
+      throw new YarnException(
+          "SubCluster " + request.getSubClusterId().toString() + " not found");
+    } else {
+      subClusterInfo.setState(request.getState());
+    }
+
+    return SubClusterDeregisterResponse.newInstance();
+  }
+
+  @Override
+  public SubClusterHeartbeatResponse subClusterHeartbeat(
+      SubClusterHeartbeatRequest request) throws YarnException {
+
+    SubClusterId subClusterId = request.getSubClusterId();
+    SubClusterInfo subClusterInfo = membership.get(subClusterId);
+
+    if (subClusterInfo == null) {
+      throw new YarnException("Subcluster " + subClusterId.toString()
+          + " does not exist; cannot heartbeat");
+    }
+
+    subClusterInfo.setLastHeartBeat(clock.getTime());
+    subClusterInfo.setState(request.getState());
+    subClusterInfo.setCapability(request.getCapability());
+
+    return SubClusterHeartbeatResponse.newInstance();
+  }
+
+  @Override
+  public GetSubClusterInfoResponse getSubCluster(
+      GetSubClusterInfoRequest request) throws YarnException {
+    SubClusterId subClusterId = request.getSubClusterId();
+    if (!membership.containsKey(subClusterId)) {
+      throw new YarnException(
+          "Subcluster " + subClusterId.toString() + " does not exist");
+    }
+
+    return GetSubClusterInfoResponse.newInstance(membership.get(subClusterId));
+  }
+
+  @Override
+  public GetSubClustersInfoResponse getSubClusters(
+      GetSubClustersInfoRequest request) throws YarnException {
+    List<SubClusterInfo> result = new ArrayList<SubClusterInfo>();
+
+    for (SubClusterInfo info : membership.values()) {
+      if (!request.getFilterInactiveSubClusters()
+          || info.getState().isActive()) {
+        result.add(info);
+      }
+    }
+    return GetSubClustersInfoResponse.newInstance(result);
+
+  }
+
+  @VisibleForTesting
+  public Map<SubClusterId, SubClusterInfo> getMembershipTable() {
+    return membership;
+  }
+
+  @VisibleForTesting
+  public void clearMembershipTable() {
+    membership.clear();
+  }
+
+}
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/store/impl/package-info.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/store/impl/package-info.java
new file mode 100644
index 00000000000..56e1274bb66
--- /dev/null
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/store/impl/package-info.java
@@ -0,0 +1,17 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership.  The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "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.
+ */
+package org.apache.hadoop.yarn.server.federation.store.impl;
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/store/records/GetSubClustersInfoRequest.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/store/records/GetSubClustersInfoRequest.java
index 3264d8188bd..90d2f99f5dd 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/store/records/GetSubClustersInfoRequest.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/store/records/GetSubClustersInfoRequest.java
@@ -26,6 +26,10 @@
 /**
  * Request class to obtain information about all sub-clusters that are
  * participating in federation.
+ *
+ * If filterInactiveSubClusters is set to true, only active sub-clusters will be
+ * returned; otherwise, all sub-clusters will be returned regardless of state.
+ * By default, filterInactiveSubClusters is true.
  */
 @Private
 @Unstable
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/store/records/SubClusterState.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/store/records/SubClusterState.java
index 22cec99b9c1..ff49aaacea8 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/store/records/SubClusterState.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/store/records/SubClusterState.java
@@ -53,6 +53,10 @@ public boolean isUnusable() {
     return (this != SC_RUNNING && this != SC_NEW);
   }
 
+  public boolean isActive() {
+    return this == SC_RUNNING;
+  }
+
   public boolean isFinal() {
     return (this == SC_UNREGISTERED || this == SC_DECOMMISSIONED
         || this == SC_LOST);
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/test/java/org/apache/hadoop/yarn/server/federation/store/impl/FederationStateStoreBaseTest.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/test/java/org/apache/hadoop/yarn/server/federation/store/impl/FederationStateStoreBaseTest.java
new file mode 100644
index 00000000000..7eb1c863292
--- /dev/null
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/test/java/org/apache/hadoop/yarn/server/federation/store/impl/FederationStateStoreBaseTest.java
@@ -0,0 +1,221 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership.  The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "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.
+ */
+
+package org.apache.hadoop.yarn.server.federation.store.impl;
+
+import java.io.IOException;
+
+import org.junit.Before;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Map;
+
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterId;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterState;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterDeregisterRequest;
+import org.apache.hadoop.yarn.exceptions.YarnException;
+import org.apache.hadoop.yarn.server.federation.store.FederationMembershipStateStore;
+import org.apache.hadoop.yarn.server.federation.store.records.GetSubClusterInfoRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.GetSubClustersInfoRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterHeartbeatRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterRegisterRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterRegisterResponse;
+import org.apache.hadoop.yarn.util.MonotonicClock;
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Base class for FederationMembershipStateStore implementations.
+ */
+public abstract class FederationStateStoreBaseTest {
+
+  static final Logger LOG =
+      LoggerFactory.getLogger(FederationStateStoreBaseTest.class);
+  private static final MonotonicClock CLOCK = new MonotonicClock();
+
+  private FederationMembershipStateStore stateStore = getStateStore();
+
+  @Before
+  public void before() throws IOException {
+    clearMembership();
+  }
+
+  @Test
+  public void testRegisterSubCluster() throws Exception {
+    SubClusterId subClusterId = SubClusterId.newInstance("SC");
+    SubClusterInfo subClusterInfo = createSubClusterInfo(subClusterId);
+
+    SubClusterRegisterResponse result = stateStore.registerSubCluster(
+        SubClusterRegisterRequest.newInstance(subClusterInfo));
+    Map<SubClusterId, SubClusterInfo> membership = getMembership();
+
+    Assert.assertNotNull(membership.get(subClusterId));
+    Assert.assertNotNull(result);
+    Assert.assertEquals(subClusterInfo, membership.get(subClusterId));
+  }
+
+  @Test
+  public void testDeregisterSubCluster() throws Exception {
+    SubClusterId subClusterId = SubClusterId.newInstance("SC");
+    SubClusterInfo subClusterInfo = createSubClusterInfo(subClusterId);
+
+    stateStore.registerSubCluster(
+        SubClusterRegisterRequest.newInstance(subClusterInfo));
+
+    SubClusterDeregisterRequest deregisterRequest = SubClusterDeregisterRequest
+        .newInstance(subClusterId, SubClusterState.SC_UNREGISTERED);
+
+    stateStore.deregisterSubCluster(deregisterRequest);
+
+    Map<SubClusterId, SubClusterInfo> membership = getMembership();
+    Assert.assertNotNull(membership.get(subClusterId));
+    Assert.assertEquals(membership.get(subClusterId).getState(),
+        SubClusterState.SC_UNREGISTERED);
+  }
+
+  @Test
+  public void testDeregisterSubClusterUnknownSubCluster() throws Exception {
+    SubClusterId subClusterId = SubClusterId.newInstance("SC");
+
+    SubClusterDeregisterRequest deregisterRequest = SubClusterDeregisterRequest
+        .newInstance(subClusterId, SubClusterState.SC_UNREGISTERED);
+    try {
+      stateStore.deregisterSubCluster(deregisterRequest);
+      Assert.fail();
+    } catch (YarnException e) {
+      Assert.assertTrue(e.getMessage().startsWith("SubCluster SC not found"));
+    }
+  }
+
+  @Test
+  public void testGetSubClusterInfo() throws Exception {
+
+    SubClusterId subClusterId = SubClusterId.newInstance("SC");
+    SubClusterInfo subClusterInfo = createSubClusterInfo(subClusterId);
+
+    stateStore.registerSubCluster(
+        SubClusterRegisterRequest.newInstance(subClusterInfo));
+
+    GetSubClusterInfoRequest request =
+        GetSubClusterInfoRequest.newInstance(subClusterId);
+    Assert.assertEquals(subClusterInfo,
+        stateStore.getSubCluster(request).getSubClusterInfo());
+  }
+
+  @Test
+  public void testGetSubClusterInfoUnknownSubCluster() throws Exception {
+    SubClusterId subClusterId = SubClusterId.newInstance("SC");
+    GetSubClusterInfoRequest request =
+        GetSubClusterInfoRequest.newInstance(subClusterId);
+
+    try {
+      stateStore.getSubCluster(request).getSubClusterInfo();
+      Assert.fail();
+    } catch (YarnException e) {
+      Assert.assertTrue(
+          e.getMessage().startsWith("Subcluster SC does not exist"));
+    }
+  }
+
+  @Test
+  public void testGetAllSubClustersInfo() throws Exception {
+
+    SubClusterId subClusterId1 = SubClusterId.newInstance("SC1");
+    SubClusterInfo subClusterInfo1 = createSubClusterInfo(subClusterId1);
+
+    SubClusterId subClusterId2 = SubClusterId.newInstance("SC2");
+    SubClusterInfo subClusterInfo2 = createSubClusterInfo(subClusterId2);
+
+    stateStore.registerSubCluster(
+        SubClusterRegisterRequest.newInstance(subClusterInfo1));
+    stateStore.registerSubCluster(
+        SubClusterRegisterRequest.newInstance(subClusterInfo2));
+
+    stateStore.subClusterHeartbeat(SubClusterHeartbeatRequest
+        .newInstance(subClusterId1, SubClusterState.SC_RUNNING, ""));
+    stateStore.subClusterHeartbeat(SubClusterHeartbeatRequest
+        .newInstance(subClusterId2, SubClusterState.SC_UNHEALTHY, ""));
+
+    Assert.assertTrue(
+        stateStore.getSubClusters(GetSubClustersInfoRequest.newInstance(true))
+            .getSubClusters().contains(subClusterInfo1));
+    Assert.assertFalse(
+        stateStore.getSubClusters(GetSubClustersInfoRequest.newInstance(true))
+            .getSubClusters().contains(subClusterInfo2));
+
+    Assert.assertTrue(
+        stateStore.getSubClusters(GetSubClustersInfoRequest.newInstance(false))
+            .getSubClusters().contains(subClusterInfo1));
+    Assert.assertTrue(
+        stateStore.getSubClusters(GetSubClustersInfoRequest.newInstance(false))
+            .getSubClusters().contains(subClusterInfo2));
+  }
+
+  @Test
+  public void testSubClusterHeartbeat() throws Exception {
+    SubClusterId subClusterId = SubClusterId.newInstance("SC");
+    SubClusterInfo subClusterInfo = createSubClusterInfo(subClusterId);
+
+    stateStore.registerSubCluster(
+        SubClusterRegisterRequest.newInstance(subClusterInfo));
+
+    SubClusterHeartbeatRequest heartbeatRequest = SubClusterHeartbeatRequest
+        .newInstance(subClusterId, SubClusterState.SC_RUNNING, "cabability");
+    stateStore.subClusterHeartbeat(heartbeatRequest);
+
+    Map<SubClusterId, SubClusterInfo> membership = getMembership();
+    Assert.assertEquals(membership.get(subClusterId).getState(),
+        SubClusterState.SC_RUNNING);
+    Assert.assertNotNull(membership.get(subClusterId).getLastHeartBeat());
+  }
+
+  @Test
+  public void testSubClusterHeartbeatUnknownSubCluster() throws Exception {
+    SubClusterId subClusterId = SubClusterId.newInstance("SC");
+    SubClusterHeartbeatRequest heartbeatRequest = SubClusterHeartbeatRequest
+        .newInstance(subClusterId, SubClusterState.SC_RUNNING, "cabability");
+
+    try {
+      stateStore.subClusterHeartbeat(heartbeatRequest);
+      Assert.fail();
+    } catch (YarnException e) {
+      Assert.assertTrue(e.getMessage()
+          .startsWith("Subcluster SC does not exist; cannot heartbeat"));
+    }
+  }
+
+  private SubClusterInfo createSubClusterInfo(SubClusterId subClusterId) {
+
+    String amRMAddress = "1.2.3.4:1";
+    String clientRMAddress = "1.2.3.4:2";
+    String rmAdminAddress = "1.2.3.4:3";
+    String webAppAddress = "1.2.3.4:4";
+
+    return SubClusterInfo.newInstance(subClusterId, amRMAddress,
+        clientRMAddress, rmAdminAddress, webAppAddress, SubClusterState.SC_NEW,
+        CLOCK.getTime(), "cabability");
+  }
+
+  protected abstract Map<SubClusterId, SubClusterInfo> getMembership();
+
+  protected abstract void clearMembership();
+
+  protected abstract FederationMembershipStateStore getStateStore();
+
+}
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/test/java/org/apache/hadoop/yarn/server/federation/store/impl/TestMemoryFederationStateStore.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/test/java/org/apache/hadoop/yarn/server/federation/store/impl/TestMemoryFederationStateStore.java
new file mode 100644
index 00000000000..b74ffbd7c89
--- /dev/null
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/test/java/org/apache/hadoop/yarn/server/federation/store/impl/TestMemoryFederationStateStore.java
@@ -0,0 +1,49 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership.  The ASF
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "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.
+ */
+
+package org.apache.hadoop.yarn.server.federation.store.impl;
+
+import java.util.Map;
+
+import org.apache.hadoop.yarn.server.federation.store.FederationMembershipStateStore;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterId;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterInfo;
+
+/**
+ * Unit tests for MemoryFederationStateStore.
+ */
+public class TestMemoryFederationStateStore
+    extends FederationStateStoreBaseTest {
+
+  private static final MemoryFederationStateStore STATESTORE =
+      new MemoryFederationStateStore();
+
+  @Override
+  protected Map<SubClusterId, SubClusterInfo> getMembership() {
+    return STATESTORE.getMembershipTable();
+  }
+
+  @Override
+  protected void clearMembership() {
+    STATESTORE.clearMembershipTable();
+  }
+
+  @Override
+  protected FederationMembershipStateStore getStateStore() {
+    return STATESTORE;
+  }
+}