diff --git a/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/api/group/GroupsIT.java b/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/api/group/GroupsIT.java
index 620b9ea..f98e588 100644
--- a/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/api/group/GroupsIT.java
+++ b/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/api/group/GroupsIT.java
@@ -45,12 +45,9 @@
 
 import java.sql.Timestamp;
 import java.util.Arrays;
-import java.util.Collections;
-import java.util.Comparator;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
-import java.util.stream.StreamSupport;
 
 @NoHttpd
 public class GroupsIT extends AbstractDaemonTest {
@@ -399,12 +396,10 @@
 
   @Test
   public void testListAllGroups() throws Exception {
-    List<String> expectedGroups =
-        StreamSupport.stream(groupCache.all().spliterator(), false)
+    List<String> expectedGroups = groupCache.all().stream()
           .map(a -> a.getName())
+          .sorted()
           .collect(toList());
-    Collections.sort(expectedGroups, Comparator.naturalOrder());
-
     assertThat(expectedGroups.size()).isAtLeast(2);
     assertThat(gApi.groups().list().getAsMap().keySet())
         .containsExactlyElementsIn(expectedGroups).inOrder();
diff --git a/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/config/ServerInfoIT.java b/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/config/ServerInfoIT.java
index ce7e8c9..a252aeb 100644
--- a/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/config/ServerInfoIT.java
+++ b/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/config/ServerInfoIT.java
@@ -66,7 +66,6 @@
     @GerritConfig(name = "gerrit.allProjects", value = "Root"),
     @GerritConfig(name = "gerrit.allUsers", value = "Users"),
     @GerritConfig(name = "gerrit.enableGwtUi", value = "true"),
-    @GerritConfig(name = "gerrit.enablePolyGerrit", value = "true"),
     @GerritConfig(name = "gerrit.reportBugText", value = "REPORT BUG"),
     @GerritConfig(name = "gerrit.reportBugUrl", value = "https://example.com/report"),
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/account/GroupCache.java b/gerrit-server/src/main/java/com/google/gerrit/server/account/GroupCache.java
index c7a2241..3d966d2 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/account/GroupCache.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/account/GroupCache.java
@@ -14,6 +14,7 @@
 
 package com.google.gerrit.server.account;
 
+import com.google.common.collect.ImmutableList;
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.reviewdb.client.AccountGroup;
 
@@ -31,8 +32,8 @@
   @Nullable
   AccountGroup get(AccountGroup.UUID uuid);
 
-  /** @return sorted iteration of groups. */
-  Iterable<AccountGroup> all();
+  /** @return sorted list of groups. */
+  ImmutableList<AccountGroup> all();
 
   /** Notify the cache that a new group was constructed. */
   void onCreateGroup(AccountGroup.NameKey newGroupName);
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/account/GroupCacheImpl.java b/gerrit-server/src/main/java/com/google/gerrit/server/account/GroupCacheImpl.java
index a2f4b65..4f5cc2b 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/account/GroupCacheImpl.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/account/GroupCacheImpl.java
@@ -16,6 +16,7 @@
 
 import com.google.common.cache.CacheLoader;
 import com.google.common.cache.LoadingCache;
+import com.google.common.collect.ImmutableList;
 import com.google.gerrit.reviewdb.client.AccountGroup;
 import com.google.gerrit.reviewdb.client.AccountGroupName;
 import com.google.gerrit.reviewdb.server.ReviewDb;
@@ -32,7 +33,6 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 import java.util.concurrent.ExecutionException;
@@ -151,12 +151,12 @@
   }
 
   @Override
-  public Iterable<AccountGroup> all() {
+  public ImmutableList<AccountGroup> all() {
     try (ReviewDb db = schema.open()) {
-      return Collections.unmodifiableList(db.accountGroups().all().toList());
+      return ImmutableList.copyOf(db.accountGroups().all());
     } catch (OrmException e) {
       log.warn("Cannot list internal groups", e);
-      return Collections.emptyList();
+      return ImmutableList.of();
     }
   }
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/account/InternalGroupBackend.java b/gerrit-server/src/main/java/com/google/gerrit/server/account/InternalGroupBackend.java
index 84660ec..2028654 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/account/InternalGroupBackend.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/account/InternalGroupBackend.java
@@ -28,7 +28,6 @@
 import org.eclipse.jgit.lib.ObjectId;
 
 import java.util.Collection;
-import java.util.stream.StreamSupport;
 
 /** Implementation of GroupBackend for the internal group system. */
 @Singleton
@@ -68,7 +67,7 @@
   @Override
   public Collection<GroupReference> suggest(final String name,
       final ProjectControl project) {
-    return StreamSupport.stream(groupCache.all().spliterator(), false)
+    return groupCache.all().stream()
         .filter(group ->
             // startsWithIgnoreCase && isVisible
             group.getName().regionMatches(true, 0, name, 0, name.length())
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/config/GerritOptions.java b/gerrit-server/src/main/java/com/google/gerrit/server/config/GerritOptions.java
index c181f79..ab4b463 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/config/GerritOptions.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/config/GerritOptions.java
@@ -33,7 +33,7 @@
       boolean forcePolyGerritDev) {
     this.slave = slave;
     this.enablePolyGerrit = forcePolyGerritDev
-        || cfg.getBoolean("gerrit", null, "enablePolyGerrit", false);
+        || cfg.getBoolean("gerrit", null, "enablePolyGerrit", true);
     this.enableGwtUi = cfg.getBoolean("gerrit", null, "enableGwtUi", true);
     this.forcePolyGerritDev = forcePolyGerritDev;
     this.headless = headless || (!enableGwtUi && !enablePolyGerrit);
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/group/ListGroups.java b/gerrit-server/src/main/java/com/google/gerrit/server/group/ListGroups.java
index d23cac4..85c3d15 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/group/ListGroups.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/group/ListGroups.java
@@ -45,6 +45,7 @@
 import org.kohsuke.args4j.Option;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.EnumSet;
 import java.util.HashMap;
@@ -314,11 +315,11 @@
     return groups;
   }
 
-  private List<AccountGroup> filterGroups(final Iterable<AccountGroup> groups) {
-    final List<AccountGroup> filteredGroups = new ArrayList<>();
-    final boolean isAdmin =
+  private List<AccountGroup> filterGroups(Collection<AccountGroup> groups) {
+    List<AccountGroup> filteredGroups = new ArrayList<>(groups.size());
+    boolean isAdmin =
         identifiedUser.get().getCapabilities().canAdministrateServer();
-    for (final AccountGroup group : groups) {
+    for (AccountGroup group : groups) {
       if (!Strings.isNullOrEmpty(matchSubstring)) {
         if (!group.getName().toLowerCase(Locale.US)
             .contains(matchSubstring.toLowerCase(Locale.US))) {
@@ -326,7 +327,7 @@
         }
       }
       if (!isAdmin) {
-        final GroupControl c = groupControlFactory.controlFor(group);
+        GroupControl c = groupControlFactory.controlFor(group);
         if (!c.isVisible()) {
           continue;
         }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeData.java b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeData.java
index eaec021..3387f06 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeData.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeData.java
@@ -17,11 +17,10 @@
 import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.base.Preconditions.checkState;
 import static com.google.gerrit.server.ApprovalsUtil.sortApprovals;
+import static java.util.stream.Collectors.toList;
 
 import com.google.auto.value.AutoValue;
 import com.google.common.base.MoreObjects;
-import com.google.common.base.Predicate;
-import com.google.common.collect.FluentIterable;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableListMultimap;
 import com.google.common.collect.ImmutableMultimap;
@@ -94,6 +93,8 @@
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
+import java.util.function.Predicate;
+import java.util.stream.Collectors;
 
 public class ChangeData {
   private static final int BATCH_SIZE = 50;
@@ -108,12 +109,8 @@
   }
 
   public static Map<Change.Id, ChangeData> asMap(List<ChangeData> changes) {
-    Map<Change.Id, ChangeData> result =
-        Maps.newHashMapWithExpectedSize(changes.size());
-    for (ChangeData cd : changes) {
-      result.put(cd.getId(), cd);
-    }
-    return result;
+    return changes.stream().collect(
+        Collectors.toMap(ChangeData::getId, cd -> cd));
   }
 
   public static void ensureChangeLoaded(Iterable<ChangeData> changes)
@@ -898,14 +895,14 @@
    * @throws OrmException an error occurred reading the database.
    */
   public Collection<PatchSet> visiblePatchSets() throws OrmException {
-    Predicate<PatchSet> predicate = ps -> {
+    Predicate<? super PatchSet> predicate = ps -> {
       try {
         return changeControl().isPatchVisible(ps, db);
       } catch (OrmException e) {
         return false;
       }
     };
-    return FluentIterable.from(patchSets()).filter(predicate).toList();
+    return patchSets().stream().filter(predicate).collect(toList());
   }
 
   public void setPatchSets(Collection<PatchSet> patchSets) {
diff --git a/gerrit-server/src/test/java/com/google/gerrit/server/query/account/AbstractQueryAccountsTest.java b/gerrit-server/src/test/java/com/google/gerrit/server/query/account/AbstractQueryAccountsTest.java
index 5686dc3..1ff5aac 100644
--- a/gerrit-server/src/test/java/com/google/gerrit/server/query/account/AbstractQueryAccountsTest.java
+++ b/gerrit-server/src/test/java/com/google/gerrit/server/query/account/AbstractQueryAccountsTest.java
@@ -36,6 +36,8 @@
 import com.google.gerrit.server.account.AuthRequest;
 import com.google.gerrit.server.query.change.InternalChangeQuery;
 import com.google.gerrit.server.schema.SchemaCreator;
+import com.google.gerrit.server.util.ManualRequestContext;
+import com.google.gerrit.server.util.OneOffRequestContext;
 import com.google.gerrit.server.util.RequestContext;
 import com.google.gerrit.server.util.ThreadLocalRequestContext;
 import com.google.gerrit.testutil.ConfigSuite;
@@ -97,6 +99,9 @@
   @Inject
   protected ThreadLocalRequestContext requestContext;
 
+  @Inject
+  protected OneOffRequestContext oneOffRequestContext;
+
   protected LifecycleManager lifecycle;
   protected ReviewDb db;
   protected AccountInfo currentUserInfo;
@@ -405,18 +410,20 @@
 
   private Account.Id createAccount(String username, String fullName,
       String email, boolean active) throws Exception {
-    Account.Id id =
-        accountManager.authenticate(AuthRequest.forUser(username)).getAccountId();
-    if (email != null) {
-      accountManager.link(id, AuthRequest.forEmail(email));
+    try (ManualRequestContext ctx = oneOffRequestContext.open()) {
+      Account.Id id =
+          accountManager.authenticate(AuthRequest.forUser(username)).getAccountId();
+      if (email != null) {
+        accountManager.link(id, AuthRequest.forEmail(email));
+      }
+      Account a = db.accounts().get(id);
+      a.setFullName(fullName);
+      a.setPreferredEmail(email);
+      a.setActive(active);
+      db.accounts().update(ImmutableList.of(a));
+      accountCache.evict(id);
+      return id;
     }
-    Account a = db.accounts().get(id);
-    a.setFullName(fullName);
-    a.setPreferredEmail(email);
-    a.setActive(active);
-    db.accounts().update(ImmutableList.of(a));
-    accountCache.evict(id);
-    return id;
   }
 
   private void addEmails(AccountInfo account, String... emails)