diff --git a/Documentation/config-gerrit.txt b/Documentation/config-gerrit.txt
index 9eded88..8ad5b9d 100644
--- a/Documentation/config-gerrit.txt
+++ b/Documentation/config-gerrit.txt
@@ -2317,6 +2317,25 @@
 +
 By default unset.
 
+[[gerrit.installIndexModule]]gerrit.installIndexModule::
++
+Class name of the Guice modules to load as alternate implementation
+for the Gerrit indexes backend.
+Classes are resolved using the primary Gerrit class loader, hence the
+class needs to be either declared in Gerrit or an additional JAR
+located under the `/lib` directory.
++
+NOTE: The `gerrit.installIndexModule` has precedence over the
+`index.type`.
++
+By default unset.
++
+Example:
+----
+[gerrit]
+  installIndexModule = com.google.gerrit.elasticsearch.ElasticIndexModule
+----
++
 [[gerrit.installModule]]gerrit.installModule::
 +
 Repeatable list of class name of additional Guice modules to load at
@@ -3136,16 +3155,13 @@
 
 [[index.type]]index.type::
 +
-Type of secondary indexing employed by Gerrit.  The supported
-values are:
+*(DEPRECATED)* The only supported value is `LUCENE`, which is the default,
+that means a link:http://lucene.apache.org/[Lucene]
+index is used.
 +
-* `LUCENE`
+For using other indexing backends (e.g. ElasticSearch), refer to
+`gerrit.installIndexModule` setting.
 +
-A link:http://lucene.apache.org/[Lucene] index is used.
-+
-+
-By default, `LUCENE`.
-
 [[index.threads]]index.threads::
 +
 Number of threads to use for indexing in normal interactive operations. Setting
diff --git a/java/com/google/gerrit/httpd/init/WebAppInitializer.java b/java/com/google/gerrit/httpd/init/WebAppInitializer.java
index 9d5e5d5..68cf1b2 100644
--- a/java/com/google/gerrit/httpd/init/WebAppInitializer.java
+++ b/java/com/google/gerrit/httpd/init/WebAppInitializer.java
@@ -292,7 +292,7 @@
     modules.add(new AuthConfigModule());
     return cfgInjector.createChildInjector(
         ModuleOverloader.override(
-            modules, LibModuleLoader.loadModules(cfgInjector, LibModuleType.DB_MODULE)));
+            modules, LibModuleLoader.loadModules(cfgInjector, LibModuleType.DB_MODULE_TYPE)));
   }
 
   private Injector createSysInjector() {
@@ -362,7 +362,7 @@
     modules.add(new ExternalIdCaseSensitivityMigrator.ExternalIdCaseSensitivityMigratorModule());
     return dbInjector.createChildInjector(
         ModuleOverloader.override(
-            modules, LibModuleLoader.loadModules(cfgInjector, LibModuleType.SYS_MODULE)));
+            modules, LibModuleLoader.loadModules(cfgInjector, LibModuleType.SYS_MODULE_TYPE)));
   }
 
   private Module createIndexModule() {
diff --git a/java/com/google/gerrit/lucene/LuceneChangeIndex.java b/java/com/google/gerrit/lucene/LuceneChangeIndex.java
index e986d40..e7d47d0 100644
--- a/java/com/google/gerrit/lucene/LuceneChangeIndex.java
+++ b/java/com/google/gerrit/lucene/LuceneChangeIndex.java
@@ -254,8 +254,6 @@
 
   @Override
   public void insert(ChangeData cd) {
-    @SuppressWarnings("unused") // TODO: Why do we need to find the lucene id?
-    Term id = LuceneChangeIndex.idTerm(idTerm, idField, cd);
     // toDocument is essentially static and doesn't depend on the specific
     // sub-index, so just pick one.
     Document doc = openIndex.toDocument(cd);
diff --git a/java/com/google/gerrit/pgm/Daemon.java b/java/com/google/gerrit/pgm/Daemon.java
index ba367ac..d77daa1 100644
--- a/java/com/google/gerrit/pgm/Daemon.java
+++ b/java/com/google/gerrit/pgm/Daemon.java
@@ -522,7 +522,9 @@
     modules.add(new LocalMergeSuperSetComputationModule());
     modules.add(new DefaultProjectNameLockManagerModule());
 
-    List<Module> libModules = LibModuleLoader.loadModules(cfgInjector, LibModuleType.SYS_MODULE);
+    List<Module> libModules =
+        LibModuleLoader.loadModules(cfgInjector, LibModuleType.SYS_MODULE_TYPE);
+    libModules.addAll(LibModuleLoader.loadModules(cfgInjector, LibModuleType.INDEX_MODULE_TYPE));
     libModules.addAll(testSysModules);
 
     AuthConfig authConfig = cfgInjector.getInstance(AuthConfig.class);
diff --git a/java/com/google/gerrit/pgm/Reindex.java b/java/com/google/gerrit/pgm/Reindex.java
index b4b5ffb..69c7d6f 100644
--- a/java/com/google/gerrit/pgm/Reindex.java
+++ b/java/com/google/gerrit/pgm/Reindex.java
@@ -30,6 +30,8 @@
 import com.google.gerrit.lucene.LuceneIndexModule;
 import com.google.gerrit.pgm.util.BatchProgramModule;
 import com.google.gerrit.pgm.util.SiteProgram;
+import com.google.gerrit.server.LibModuleLoader;
+import com.google.gerrit.server.ModuleOverloader;
 import com.google.gerrit.server.cache.CacheDisplay;
 import com.google.gerrit.server.cache.CacheInfo;
 import com.google.gerrit.server.change.ChangeResource;
@@ -207,7 +209,9 @@
           }
         });
 
-    return dbInjector.createChildInjector(modules);
+    return dbInjector.createChildInjector(
+        ModuleOverloader.override(
+            modules, LibModuleLoader.loadReindexModules(cfgInjector, versions, threads, replica)));
   }
 
   private void overrideConfig() {
diff --git a/java/com/google/gerrit/pgm/util/BatchProgramModule.java b/java/com/google/gerrit/pgm/util/BatchProgramModule.java
index 64eef05..9bd3067 100644
--- a/java/com/google/gerrit/pgm/util/BatchProgramModule.java
+++ b/java/com/google/gerrit/pgm/util/BatchProgramModule.java
@@ -214,7 +214,8 @@
     bind(AccountVisibility.class).toProvider(AccountVisibilityProvider.class).in(SINGLETON);
 
     ModuleOverloader.override(
-            modules, LibModuleLoader.loadModules(parentInjector, LibModuleType.SYS_BATCH_MODULE))
+            modules,
+            LibModuleLoader.loadModules(parentInjector, LibModuleType.SYS_BATCH_MODULE_TYPE))
         .stream()
         .forEach(this::install);
   }
diff --git a/java/com/google/gerrit/pgm/util/SiteProgram.java b/java/com/google/gerrit/pgm/util/SiteProgram.java
index ed6bce6..ff0b31e 100644
--- a/java/com/google/gerrit/pgm/util/SiteProgram.java
+++ b/java/com/google/gerrit/pgm/util/SiteProgram.java
@@ -137,7 +137,7 @@
       return Guice.createInjector(
           PRODUCTION,
           ModuleOverloader.override(
-              modules, LibModuleLoader.loadModules(cfgInjector, LibModuleType.DB_MODULE)));
+              modules, LibModuleLoader.loadModules(cfgInjector, LibModuleType.DB_MODULE_TYPE)));
     } catch (CreationException ce) {
       Message first = ce.getErrorMessages().iterator().next();
       Throwable why = first.getCause();
diff --git a/java/com/google/gerrit/server/LibModuleLoader.java b/java/com/google/gerrit/server/LibModuleLoader.java
index 0a6fb9f..36765e9 100644
--- a/java/com/google/gerrit/server/LibModuleLoader.java
+++ b/java/com/google/gerrit/server/LibModuleLoader.java
@@ -22,8 +22,10 @@
 import com.google.inject.Key;
 import com.google.inject.Module;
 import com.google.inject.ProvisionException;
+import java.lang.reflect.Method;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Map;
 import org.eclipse.jgit.lib.Config;
 
 /** Loads configured Guice modules from {@code gerrit.installModule}. */
@@ -37,6 +39,33 @@
         .collect(toList());
   }
 
+  public static List<Module> loadReindexModules(
+      Injector parent, Map<String, Integer> versions, int threads, boolean replica) {
+    Config cfg = getConfig(parent);
+    return Arrays.stream(
+            cfg.getStringList(
+                "gerrit", null, "install" + LibModuleType.INDEX_MODULE_TYPE.getConfigKey()))
+        .map(m -> createReindexModule(m, versions, threads, replica))
+        .collect(toList());
+  }
+
+  private static Module createReindexModule(
+      String className, Map<String, Integer> versions, int threads, boolean replica) {
+    Class<Module> clazz = loadModule(className);
+    try {
+
+      Method m =
+          clazz.getMethod("singleVersionWithExplicitVersions", Map.class, int.class, boolean.class);
+
+      Module module = (Module) m.invoke(null, versions, threads, replica);
+      logger.atInfo().log("Installed module %s", className);
+      return module;
+    } catch (Exception e) {
+      logger.atSevere().withCause(e).log("Unable to load libModule for %s", className);
+      throw new IllegalStateException(e);
+    }
+  }
+
   private static Config getConfig(Injector i) {
     return i.getInstance(Key.get(Config.class, GerritServerConfig.class));
   }
diff --git a/java/com/google/gerrit/server/LibModuleType.java b/java/com/google/gerrit/server/LibModuleType.java
index b9cb196..57206aa 100644
--- a/java/com/google/gerrit/server/LibModuleType.java
+++ b/java/com/google/gerrit/server/LibModuleType.java
@@ -18,13 +18,16 @@
 public enum LibModuleType {
 
   /** Module for the sysInjector. */
-  SYS_MODULE("Module"),
+  SYS_MODULE_TYPE("Module"),
 
   /** BatchModule for the sysInjector */
-  SYS_BATCH_MODULE("BatchModule"),
+  SYS_BATCH_MODULE_TYPE("BatchModule"),
 
   /** Module for the dbInjector. */
-  DB_MODULE("DbModule");
+  DB_MODULE_TYPE("DbModule"),
+
+  /** Module for the implementation of the indexing backend. */
+  INDEX_MODULE_TYPE("IndexModule");
 
   private final String configKey;
 
diff --git a/javatests/com/google/gerrit/acceptance/rest/binding/PluginProvidedChildRestApiBindingsIT.java b/javatests/com/google/gerrit/acceptance/rest/binding/PluginProvidedChildRestApiBindingsIT.java
index 23a1d23..d2c1430 100644
--- a/javatests/com/google/gerrit/acceptance/rest/binding/PluginProvidedChildRestApiBindingsIT.java
+++ b/javatests/com/google/gerrit/acceptance/rest/binding/PluginProvidedChildRestApiBindingsIT.java
@@ -56,8 +56,7 @@
   @Inject private TestCommentHelper testCommentHelper;
 
   /** Resource to bind a child collection. */
-  public static final TypeLiteral<RestView<TestPluginResource>> TEST_KIND =
-      new TypeLiteral<RestView<TestPluginResource>>() {};
+  public static final TypeLiteral<RestView<TestPluginResource>> TEST_KIND = new TypeLiteral<>() {};
 
   private static final String PLUGIN_NAME = "my-plugin";
 
diff --git a/javatests/com/google/gerrit/acceptance/rest/binding/PluginProvidedRootRestApiBindingsIT.java b/javatests/com/google/gerrit/acceptance/rest/binding/PluginProvidedRootRestApiBindingsIT.java
index 16dc294..24ce605 100644
--- a/javatests/com/google/gerrit/acceptance/rest/binding/PluginProvidedRootRestApiBindingsIT.java
+++ b/javatests/com/google/gerrit/acceptance/rest/binding/PluginProvidedRootRestApiBindingsIT.java
@@ -60,8 +60,7 @@
 public class PluginProvidedRootRestApiBindingsIT extends AbstractDaemonTest {
 
   /** Resource to bind a child collection. */
-  public static final TypeLiteral<RestView<TestPluginResource>> TEST_KIND =
-      new TypeLiteral<RestView<TestPluginResource>>() {};
+  public static final TypeLiteral<RestView<TestPluginResource>> TEST_KIND = new TypeLiteral<>() {};
 
   private static final String PLUGIN_NAME = "my-plugin";
 
diff --git a/plugins/replication b/plugins/replication
index 756d349..4f5de60 160000
--- a/plugins/replication
+++ b/plugins/replication
@@ -1 +1 @@
-Subproject commit 756d349cb3a16652568aad46b34f2eb9c3d04a36
+Subproject commit 4f5de60081d7c098d09c842e3ea9d5bc920df71b
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-builder/token-highlight-layer.ts b/polygerrit-ui/app/elements/diff/gr-diff-builder/token-highlight-layer.ts
index de7d007..b7d77cb3 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-builder/token-highlight-layer.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-builder/token-highlight-layer.ts
@@ -39,7 +39,7 @@
 /** CSS class for the currently hovered token. */
 const CSS_HIGHLIGHT = 'token-highlight';
 
-export const HOVER_DELAY_MS = 200;
+export const HOVER_DELAY_MS = 500;
 
 const LINE_LENGTH_LIMIT = 500;
 
diff --git a/polygerrit-ui/app/utils/dom-util.ts b/polygerrit-ui/app/utils/dom-util.ts
index e2fa8fe..dd408d3 100644
--- a/polygerrit-ui/app/utils/dom-util.ts
+++ b/polygerrit-ui/app/utils/dom-util.ts
@@ -452,7 +452,10 @@
     // Suppress shortcuts if the key is 'enter'
     // and target is an anchor or button or paper-tab.
     (e.keyCode === 13 &&
-      (tagName === 'A' || tagName === 'BUTTON' || tagName === 'PAPER-TAB'))
+      (tagName === 'A' ||
+        tagName === 'BUTTON' ||
+        tagName === 'GR-BUTTON' ||
+        tagName === 'PAPER-TAB'))
   ) {
     return true;
   }
diff --git a/polygerrit-ui/app/utils/dom-util_test.ts b/polygerrit-ui/app/utils/dom-util_test.ts
index 9dd5be2..5429550 100644
--- a/polygerrit-ui/app/utils/dom-util_test.ts
+++ b/polygerrit-ui/app/utils/dom-util_test.ts
@@ -320,6 +320,15 @@
       });
     });
 
+    test('suppress "enter" shortcut event from <gr-button>', async () => {
+      await keyEventOn(
+        document.createElement('gr-button'),
+        e => assert.isTrue(shouldSuppress(e)),
+        13,
+        'enter'
+      );
+    });
+
     test('suppress "enter" shortcut event from <a>', async () => {
       await keyEventOn(document.createElement('a'), e => {
         assert.isFalse(shouldSuppress(e));
diff --git a/tools/maven/gerrit-acceptance-framework_pom.xml b/tools/maven/gerrit-acceptance-framework_pom.xml
index 3705407..d3e6faa 100644
--- a/tools/maven/gerrit-acceptance-framework_pom.xml
+++ b/tools/maven/gerrit-acceptance-framework_pom.xml
@@ -77,6 +77,9 @@
       <name>Patrick Hiesel</name>
     </developer>
     <developer>
+      <name>Patrick Mulhall</name>
+    </developer>
+    <developer>
       <name>Saša Živkov</name>
     </developer>
     <developer>
@@ -85,6 +88,9 @@
     <developer>
       <name>Tao Zhou</name>
     </developer>
+    <developer>
+      <name>Thomas Dräbing</name>
+    </developer>
   </developers>
 
   <mailingLists>
diff --git a/tools/maven/gerrit-extension-api_pom.xml b/tools/maven/gerrit-extension-api_pom.xml
index ba35ca2..34def36 100644
--- a/tools/maven/gerrit-extension-api_pom.xml
+++ b/tools/maven/gerrit-extension-api_pom.xml
@@ -77,6 +77,9 @@
       <name>Patrick Hiesel</name>
     </developer>
     <developer>
+      <name>Patrick Mulhall</name>
+    </developer>
+    <developer>
       <name>Saša Živkov</name>
     </developer>
     <developer>
@@ -85,6 +88,9 @@
     <developer>
       <name>Tao Zhou</name>
     </developer>
+    <developer>
+      <name>Thomas Dräbing</name>
+    </developer>
   </developers>
 
   <mailingLists>
diff --git a/tools/maven/gerrit-plugin-api_pom.xml b/tools/maven/gerrit-plugin-api_pom.xml
index b7954c7..441e4c0 100644
--- a/tools/maven/gerrit-plugin-api_pom.xml
+++ b/tools/maven/gerrit-plugin-api_pom.xml
@@ -77,6 +77,9 @@
       <name>Patrick Hiesel</name>
     </developer>
     <developer>
+      <name>Patrick Mulhall</name>
+    </developer>
+    <developer>
       <name>Saša Živkov</name>
     </developer>
     <developer>
@@ -85,6 +88,9 @@
     <developer>
       <name>Tao Zhou</name>
     </developer>
+    <developer>
+      <name>Thomas Dräbing</name>
+    </developer>
   </developers>
 
   <mailingLists>
diff --git a/tools/maven/gerrit-war_pom.xml b/tools/maven/gerrit-war_pom.xml
index 118cf39..b61d480 100644
--- a/tools/maven/gerrit-war_pom.xml
+++ b/tools/maven/gerrit-war_pom.xml
@@ -77,6 +77,9 @@
       <name>Patrick Hiesel</name>
     </developer>
     <developer>
+      <name>Patrick Mulhall</name>
+    </developer>
+    <developer>
       <name>Saša Živkov</name>
     </developer>
     <developer>
@@ -85,6 +88,9 @@
     <developer>
       <name>Tao Zhou</name>
     </developer>
+    <developer>
+      <name>Thomas Dräbing</name>
+    </developer>
   </developers>
 
   <mailingLists>