diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/ApprovalsUtil.java b/gerrit-server/src/main/java/com/google/gerrit/server/ApprovalsUtil.java
index 7b7476f..25654d2 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/ApprovalsUtil.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/ApprovalsUtil.java
@@ -19,10 +19,10 @@
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Function;
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSetMultimap;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.LinkedHashMultimap;
 import com.google.common.collect.Lists;
-import com.google.common.collect.Multimaps;
 import com.google.common.collect.Ordering;
 import com.google.common.collect.SetMultimap;
 import com.google.common.collect.Sets;
@@ -36,6 +36,7 @@
 import com.google.gerrit.reviewdb.client.PatchSetInfo;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.change.ChangeKind;
+import com.google.gerrit.server.notedb.ReviewerState;
 import com.google.gerrit.server.util.TimeUtil;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
@@ -77,21 +78,18 @@
   public ApprovalsUtil() {
   }
 
-  public static enum ReviewerState {
-    REVIEWER, CC;
-  }
-
   /**
    * Get all reviewers for a change.
    *
    * @param db review database.
    * @param changeId change ID.
    * @return multimap of reviewers keyed by state, where each account appears
-   *     exactly once in {@link SetMultimap#values()}.
+   *     exactly once in {@link SetMultimap#values()}, and
+   *     {@link ReviewerState#REMOVED} is not present.
    * @throws OrmException if reviewers for the change could not be read.
    */
-  public SetMultimap<ReviewerState, Account.Id> getReviewers(ReviewDb db,
-      Change.Id changeId) throws OrmException {
+  public ImmutableSetMultimap<ReviewerState, Account.Id> getReviewers(
+      ReviewDb db, Change.Id changeId) throws OrmException {
     return getReviewers(db.patchSetApprovals().byChange(changeId));
   }
 
@@ -101,9 +99,10 @@
    * @param allApprovals all approvals to consider; must all belong to the same
    *     change.
    * @return multimap of reviewers keyed by state, where each account appears
-   *     exactly once in {@link SetMultimap#values()}.
+   *     exactly once in {@link SetMultimap#values()}, and
+   *     {@link ReviewerState#REMOVED} is not present.
    */
-  public static SetMultimap<ReviewerState, Account.Id> getReviewers(
+  public static ImmutableSetMultimap<ReviewerState, Account.Id> getReviewers(
       Iterable<PatchSetApproval> allApprovals) {
     PatchSetApproval first = null;
     SetMultimap<ReviewerState, Account.Id> reviewers =
@@ -125,7 +124,7 @@
         reviewers.put(ReviewerState.CC, id);
       }
     }
-    return Multimaps.unmodifiableSetMultimap(reviewers);
+    return ImmutableSetMultimap.copyOf(reviewers);
   }
 
   /**
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/change/PatchSetInserter.java b/gerrit-server/src/main/java/com/google/gerrit/server/change/PatchSetInserter.java
index 99292f3..1840e76 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/change/PatchSetInserter.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/change/PatchSetInserter.java
@@ -28,7 +28,6 @@
 import com.google.gerrit.reviewdb.client.RevId;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.ApprovalsUtil;
-import com.google.gerrit.server.ApprovalsUtil.ReviewerState;
 import com.google.gerrit.server.ChangeUtil;
 import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.events.CommitReceivedEvent;
@@ -36,6 +35,7 @@
 import com.google.gerrit.server.git.validators.CommitValidationException;
 import com.google.gerrit.server.git.validators.CommitValidators;
 import com.google.gerrit.server.mail.ReplacePatchSetSender;
+import com.google.gerrit.server.notedb.ReviewerState;
 import com.google.gerrit.server.patch.PatchSetInfoFactory;
 import com.google.gerrit.server.project.ChangeControl;
 import com.google.gerrit.server.project.InvalidChangeOperationException;
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/git/ReceiveCommits.java b/gerrit-server/src/main/java/com/google/gerrit/server/git/ReceiveCommits.java
index a9710e1..59431b5 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/git/ReceiveCommits.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/git/ReceiveCommits.java
@@ -18,7 +18,6 @@
 import static com.google.gerrit.server.git.MultiProgressMonitor.UNKNOWN;
 import static com.google.gerrit.server.mail.MailUtil.getRecipientsFromFooters;
 import static com.google.gerrit.server.mail.MailUtil.getRecipientsFromReviewers;
-
 import static org.eclipse.jgit.lib.Constants.R_HEADS;
 import static org.eclipse.jgit.lib.RefDatabase.ALL;
 import static org.eclipse.jgit.transport.ReceiveCommand.Result.NOT_ATTEMPTED;
@@ -64,7 +63,6 @@
 import com.google.gerrit.reviewdb.client.RevId;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.ApprovalsUtil;
-import com.google.gerrit.server.ApprovalsUtil.ReviewerState;
 import com.google.gerrit.server.ChangeUtil;
 import com.google.gerrit.server.GerritPersonIdent;
 import com.google.gerrit.server.IdentifiedUser;
@@ -90,6 +88,7 @@
 import com.google.gerrit.server.mail.MailUtil.MailRecipients;
 import com.google.gerrit.server.mail.MergedSender;
 import com.google.gerrit.server.mail.ReplacePatchSetSender;
+import com.google.gerrit.server.notedb.ReviewerState;
 import com.google.gerrit.server.patch.PatchSetInfoFactory;
 import com.google.gerrit.server.project.ChangeControl;
 import com.google.gerrit.server.project.ProjectCache;
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/mail/ChangeEmail.java b/gerrit-server/src/main/java/com/google/gerrit/server/mail/ChangeEmail.java
index 47baa9e..09f9e42 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/mail/ChangeEmail.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/mail/ChangeEmail.java
@@ -25,9 +25,9 @@
 import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.reviewdb.client.PatchSetInfo;
 import com.google.gerrit.reviewdb.client.StarredChange;
-import com.google.gerrit.server.ApprovalsUtil.ReviewerState;
 import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.mail.ProjectWatch.Watchers;
+import com.google.gerrit.server.notedb.ReviewerState;
 import com.google.gerrit.server.patch.PatchList;
 import com.google.gerrit.server.patch.PatchListEntry;
 import com.google.gerrit.server.patch.PatchListNotAvailableException;
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/mail/MailUtil.java b/gerrit-server/src/main/java/com/google/gerrit/server/mail/MailUtil.java
index 801e599..ac367ef 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/mail/MailUtil.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/mail/MailUtil.java
@@ -18,8 +18,8 @@
 import com.google.gerrit.common.errors.NoSuchAccountException;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.PatchSet;
-import com.google.gerrit.server.ApprovalsUtil.ReviewerState;
 import com.google.gerrit.server.account.AccountResolver;
+import com.google.gerrit.server.notedb.ReviewerState;
 import com.google.gwtorm.server.OrmException;
 
 import org.eclipse.jgit.revwalk.FooterKey;
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotes.java b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotes.java
index 3438424..4d75d82 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotes.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotes.java
@@ -21,10 +21,12 @@
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Function;
 import com.google.common.collect.ArrayListMultimap;
+import com.google.common.collect.ImmutableListMultimap;
+import com.google.common.collect.ImmutableSetMultimap;
 import com.google.common.collect.ListMultimap;
 import com.google.common.collect.Maps;
-import com.google.common.collect.Multimaps;
 import com.google.common.collect.Ordering;
+import com.google.common.collect.Sets;
 import com.google.common.primitives.Ints;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Change;
@@ -41,16 +43,20 @@
 import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.eclipse.jgit.lib.CommitBuilder;
 import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.PersonIdent;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevWalk;
+import org.eclipse.jgit.util.RawParseUtils;
 
 import java.io.IOException;
 import java.sql.Timestamp;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 /** View of a single {@link Change} based on the log of its notes branch. */
 public class ChangeNotes extends VersionedMetaData {
@@ -90,8 +96,154 @@
     }
   }
 
+  private static class Parser {
+    private final Change.Id changeId;
+    private final ObjectId tip;
+    private final RevWalk walk;
+    private final ListMultimap<PatchSet.Id, PatchSetApproval> approvals;
+    private final Map<Account.Id, ReviewerState> reviewers;
+
+    private Parser(Change.Id changeId, ObjectId tip, RevWalk walk) {
+      this.changeId = changeId;
+      this.tip = tip;
+      this.walk = walk;
+      approvals = ArrayListMultimap.create();
+      reviewers = Maps.newLinkedHashMap();
+    }
+
+    private void parseAll() throws ConfigInvalidException, IOException {
+      walk.markStart(walk.parseCommit(tip));
+      for (RevCommit commit : walk) {
+        parse(commit);
+      }
+      pruneReviewers();
+      for (Collection<PatchSetApproval> v : approvals.asMap().values()) {
+        Collections.sort((List<PatchSetApproval>) v, PSA_BY_TIME);
+      }
+    }
+
+    private void parse(RevCommit commit) throws ConfigInvalidException {
+      PatchSet.Id psId = parsePatchSetId(commit);
+      Account.Id accountId = parseIdent(commit);
+      List<PatchSetApproval> psas = approvals.get(psId);
+
+      Map<String, PatchSetApproval> curr =
+          Maps.newHashMapWithExpectedSize(psas.size());
+      for (PatchSetApproval psa : psas) {
+        if (psa.getAccountId().equals(accountId)) {
+          curr.put(psa.getLabel(), psa);
+        }
+      }
+
+      for (String line : commit.getFooterLines(FOOTER_LABEL)) {
+        PatchSetApproval psa = parseApproval(psId, accountId, commit, line);
+        if (!curr.containsKey(psa.getLabel())) {
+          curr.put(psa.getLabel(), psa);
+          psas.add(psa);
+        }
+      }
+      for (ReviewerState state : ReviewerState.values()) {
+        for (String line : commit.getFooterLines(state.getFooterKey())) {
+          parseReviewer(state, line);
+        }
+      }
+    }
+
+    private PatchSet.Id parsePatchSetId(RevCommit commit)
+        throws ConfigInvalidException {
+      List<String> psIdLines = commit.getFooterLines(FOOTER_PATCH_SET);
+      if (psIdLines.size() != 1) {
+        throw parseException("missing or multiple %s: %s",
+            FOOTER_PATCH_SET, psIdLines);
+      }
+      Integer psId = Ints.tryParse(psIdLines.get(0));
+      if (psId == null) {
+        throw parseException("invalid %s: %s",
+            FOOTER_PATCH_SET, psIdLines.get(0));
+      }
+      return new PatchSet.Id(changeId, psId);
+    }
+
+    private PatchSetApproval parseApproval(PatchSet.Id psId, Account.Id accountId,
+        RevCommit commit, String line) throws ConfigInvalidException {
+      try {
+        LabelVote l = LabelVote.parseWithEquals(line);
+        return new PatchSetApproval(
+            new PatchSetApproval.Key(
+              psId, parseIdent(commit), new LabelId(l.getLabel())),
+            l.getValue(),
+            new Timestamp(commit.getCommitterIdent().getWhen().getTime()));
+      } catch (IllegalArgumentException e) {
+        ConfigInvalidException pe =
+            parseException("invalid %s: %s", FOOTER_LABEL, line);
+        pe.initCause(e);
+        throw pe;
+      }
+    }
+
+    private Account.Id parseIdent(RevCommit commit)
+        throws ConfigInvalidException {
+      return parseIdent(commit.getCommitterIdent());
+    }
+
+    private Account.Id parseIdent(PersonIdent ident)
+        throws ConfigInvalidException {
+      String email = ident.getEmailAddress();
+      int at = email.indexOf('@');
+      if (at >= 0) {
+        String host = email.substring(at + 1, email.length());
+        Integer id = Ints.tryParse(email.substring(0, at));
+        if (id != null && host.equals(GERRIT_PLACEHOLDER_HOST)) {
+          return new Account.Id(id);
+        }
+      }
+      throw parseException("invalid identity, expected <id>@%s: %s",
+        GERRIT_PLACEHOLDER_HOST, email);
+    }
+
+    private void parseReviewer(ReviewerState state, String line)
+        throws ConfigInvalidException {
+      PersonIdent ident = RawParseUtils.parsePersonIdent(line);
+      if (ident == null) {
+        throw parseException(
+            "invalid %s: %s", state.getFooterKey().getName(), line);
+      }
+      Account.Id accountId = parseIdent(ident);
+      if (!reviewers.containsKey(accountId)) {
+        reviewers.put(accountId, state);
+      }
+    }
+
+    private void pruneReviewers() {
+      Set<Account.Id> removed = Sets.newHashSetWithExpectedSize(reviewers.size());
+      Iterator<Map.Entry<Account.Id, ReviewerState>> rit =
+          reviewers.entrySet().iterator();
+      while (rit.hasNext()) {
+        Map.Entry<Account.Id, ReviewerState> e = rit.next();
+        if (e.getValue() == ReviewerState.REMOVED) {
+          removed.add(e.getKey());
+          rit.remove();
+        }
+      }
+
+      Iterator<Map.Entry<PatchSet.Id, PatchSetApproval>> ait =
+          approvals.entries().iterator();
+      while (ait.hasNext()) {
+        if (removed.contains(ait.next().getValue().getAccountId())) {
+          ait.remove();
+        }
+      }
+    }
+
+    private ConfigInvalidException parseException(String fmt, Object... args) {
+      return new ConfigInvalidException("Change " + changeId + ": "
+          + String.format(fmt, args));
+    }
+  }
+
   private final Change change;
-  private ListMultimap<PatchSet.Id, PatchSetApproval> approvals;
+  private ImmutableListMultimap<PatchSet.Id, PatchSetApproval> approvals;
+  private ImmutableSetMultimap<ReviewerState, Account.Id> reviewers;
 
   @VisibleForTesting
   ChangeNotes(Repository repo, Change change)
@@ -100,8 +252,12 @@
     load(repo);
   }
 
-  public ListMultimap<PatchSet.Id, PatchSetApproval> getApprovals() {
-    return Multimaps.unmodifiableListMultimap(approvals);
+  public ImmutableListMultimap<PatchSet.Id, PatchSetApproval> getApprovals() {
+    return approvals;
+  }
+
+  public ImmutableSetMultimap<ReviewerState, Account.Id> getReviewers() {
+    return reviewers;
   }
 
   @Override
@@ -115,89 +271,21 @@
     if (rev == null) {
       return;
     }
-    approvals = ArrayListMultimap.create();
     RevWalk walk = new RevWalk(reader);
-    walk.markStart(walk.parseCommit(rev));
-    for (RevCommit commit : walk) {
-      parse(commit);
-    }
-    for (Collection<PatchSetApproval> v : approvals.asMap().values()) {
-      Collections.sort((List<PatchSetApproval>) v, PSA_BY_TIME);
-    }
-  }
-
-  private void parse(RevCommit commit) throws ConfigInvalidException {
-    PatchSet.Id psId = parsePatchSetId(commit);
-    Account.Id accountId = parseIdent(commit);
-    List<PatchSetApproval> psas = approvals.get(psId);
-
-    Map<String, PatchSetApproval> curr =
-        Maps.newHashMapWithExpectedSize(psas.size());
-    for (PatchSetApproval psa : psas) {
-      if (psa.getAccountId().equals(accountId)) {
-        curr.put(psa.getLabel(), psa);
-      }
-    }
-
-    for (String line : commit.getFooterLines(FOOTER_LABEL)) {
-      PatchSetApproval psa = parseApproval(psId, accountId, commit, line);
-      if (!curr.containsKey(psa.getLabel())) {
-        curr.put(psa.getLabel(), psa);
-        psas.add(psa);
-      }
-    }
-  }
-
-  private PatchSet.Id parsePatchSetId(RevCommit commit)
-      throws ConfigInvalidException {
-    List<String> psIdLines = commit.getFooterLines(FOOTER_PATCH_SET);
-    if (psIdLines.size() != 1) {
-      throw parseException("missing or multiple %s: %s",
-          FOOTER_PATCH_SET, psIdLines);
-    }
-    Integer psId = Ints.tryParse(psIdLines.get(0));
-    if (psId == null) {
-      throw parseException("invalid %s: %s",
-          FOOTER_PATCH_SET, psIdLines.get(0));
-    }
-    return new PatchSet.Id(change.getId(), psId);
-  }
-
-  private PatchSetApproval parseApproval(PatchSet.Id psId, Account.Id accountId,
-      RevCommit commit, String line) throws ConfigInvalidException {
     try {
-      LabelVote l = LabelVote.parseWithEquals(line);
-      return new PatchSetApproval(
-          new PatchSetApproval.Key(
-            psId, parseIdent(commit), new LabelId(l.getLabel())),
-          l.getValue(),
-          new Timestamp(commit.getCommitterIdent().getWhen().getTime()));
-    } catch (IllegalArgumentException e) {
-      ConfigInvalidException pe =
-          parseException("invalid %s: %s", FOOTER_LABEL, line);
-      pe.initCause(e);
-      throw pe;
-    }
-  }
-
-  private Account.Id parseIdent(RevCommit commit)
-      throws ConfigInvalidException {
-    String email = commit.getCommitterIdent().getEmailAddress();
-    int at = email.indexOf('@');
-    if (at >= 0) {
-      String host = email.substring(at + 1, email.length());
-      Integer id = Ints.tryParse(email.substring(0, at));
-      if (id != null && host.equals(GERRIT_PLACEHOLDER_HOST)) {
-        return new Account.Id(id);
+      Parser parser = new Parser(change.getId(), rev, walk);
+      parser.parseAll();
+      approvals = ImmutableListMultimap.copyOf(parser.approvals);
+      ImmutableSetMultimap.Builder<ReviewerState, Account.Id> reviewers =
+          ImmutableSetMultimap.builder();
+      for (Map.Entry<Account.Id, ReviewerState> e
+          : parser.reviewers.entrySet()) {
+        reviewers.put(e.getValue(), e.getKey());
       }
+      this.reviewers = reviewers.build();
+    } finally {
+      walk.release();
     }
-    throw parseException("invalid committer, expected <id>@%s: %s",
-      GERRIT_PLACEHOLDER_HOST, email);
-  }
-
-  private ConfigInvalidException parseException(String fmt, Object... args) {
-    return new ConfigInvalidException("Change " + change.getId() + ": "
-        + String.format(fmt, args));
   }
 
   @Override
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeUpdate.java b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeUpdate.java
index 4c85435..ae7beac 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeUpdate.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeUpdate.java
@@ -28,13 +28,14 @@
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.server.GerritPersonIdent;
 import com.google.gerrit.server.IdentifiedUser;
+import com.google.gerrit.server.account.AccountCache;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.git.MetaDataUpdate;
 import com.google.gerrit.server.git.VersionedMetaData;
 import com.google.gerrit.server.project.ProjectCache;
 import com.google.gerrit.server.util.LabelVote;
-import com.google.gerrit.server.util.TimeUtil;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
 import com.google.inject.Singleton;
@@ -47,8 +48,9 @@
 import org.eclipse.jgit.revwalk.RevCommit;
 
 import java.io.IOException;
-import java.sql.Timestamp;
+import java.util.Date;
 import java.util.Map;
+import java.util.TimeZone;
 
 /**
  * A single delta to apply atomically to a change.
@@ -57,65 +59,90 @@
  * limitations on the set of modifications that can be handled in a single
  * update. In particular, there is a single author and timestamp for each
  * update.
+ * <p>
+ * This class is not thread-safe.
  */
 public class ChangeUpdate extends VersionedMetaData {
   @Singleton
   public static class Factory {
     private final GitRepositoryManager repoManager;
+    private final AccountCache accountCache;
     private final MetaDataUpdate.User updateFactory;
     private final ProjectCache projectCache;
     private final Provider<IdentifiedUser> user;
+    private final PersonIdent serverIdent;
 
     @Inject
     Factory(
         GitRepositoryManager repoManager,
+        AccountCache accountCache,
         MetaDataUpdate.User updateFactory,
         ProjectCache projectCache,
-        Provider<IdentifiedUser> user) {
+        Provider<IdentifiedUser> user,
+        @GerritPersonIdent PersonIdent serverIdent) {
       this.repoManager = repoManager;
+      this.accountCache = accountCache;
       this.updateFactory = updateFactory;
       this.projectCache = projectCache;
       this.user = user;
+      this.serverIdent = serverIdent;
     }
 
     public ChangeUpdate create(Change change) {
-      return create(change, TimeUtil.nowTs());
+      return create(change, serverIdent.getWhen());
     }
 
-    public ChangeUpdate create(Change change, Timestamp when) {
+    public ChangeUpdate create(Change change, Date when) {
       return new ChangeUpdate(
-          repoManager, updateFactory,
+          repoManager, accountCache, updateFactory,
           projectCache.get(change.getProject()).getLabelTypes(),
-          change, user.get().getAccountId(), when);
+          change, user.get().getAccount(), when, serverIdent.getTimeZone());
     }
   }
 
   private final GitRepositoryManager repoManager;
+  private final AccountCache accountCache;
   private final MetaDataUpdate.User updateFactory;
   private final LabelTypes labelTypes;
   private final Change change;
-  private final Account.Id accountId;
-  private final Timestamp when;
+  private final Account account;
+  private final Date when;
+  private final TimeZone tz;
   private final Map<String, Short> approvals;
+  private final Map<Account.Id, ReviewerState> reviewers;
   private String subject;
   private PatchSet.Id psId;
 
   @VisibleForTesting
-  ChangeUpdate(GitRepositoryManager repoManager, LabelTypes labelTypes,
-      Change change, Account.Id accountId, @Nullable Timestamp when) {
-    this(repoManager, null, labelTypes, change, accountId, when);
+  ChangeUpdate(GitRepositoryManager repoManager, AccountCache accountCache,
+      LabelTypes labelTypes, Change change, Account account, Date when,
+      TimeZone tz) {
+    this(repoManager, accountCache, null, labelTypes, change, account, when,
+        tz);
   }
 
   private ChangeUpdate(GitRepositoryManager repoManager,
-      @Nullable MetaDataUpdate.User updateFactory, LabelTypes labelTypes,
-      Change change, Account.Id accountId, @Nullable Timestamp when) {
+      AccountCache accountCache, @Nullable MetaDataUpdate.User updateFactory,
+      LabelTypes labelTypes, Change change, Account account, Date when,
+      TimeZone tz) {
     this.repoManager = repoManager;
+    this.accountCache = accountCache;
     this.updateFactory = updateFactory;
     this.labelTypes = labelTypes;
     this.change = change;
-    this.accountId = accountId;
+    this.account = account;
     this.when = when;
+    this.tz = tz;
     this.approvals = Maps.newTreeMap(labelTypes.nameComparator());
+    this.reviewers = Maps.newLinkedHashMap();
+  }
+
+  public Account getAccount() {
+    return account;
+  }
+
+  public Date getWhen() {
+    return when;
   }
 
   public void putApproval(String label, short value) {
@@ -131,6 +158,15 @@
     this.psId = psId;
   }
 
+  public void putReviewer(Account.Id reviewer, ReviewerState type) {
+    checkArgument(type != ReviewerState.REMOVED, "invalid ReviewerType");
+    reviewers.put(reviewer, type);
+  }
+
+  public void removeReviewer(Account.Id reviewer) {
+    reviewers.put(reviewer, ReviewerState.REMOVED);
+  }
+
   public RevCommit commit() throws IOException {
     return commit(checkNotNull(updateFactory, "MetaDataUpdate.Factory")
         .create(change.getProject()));
@@ -149,18 +185,21 @@
 
     md.setAllowEmpty(true);
     CommitBuilder cb = md.getCommitBuilder();
-    cb.setCommitter(new PersonIdent(
-        cb.getAuthor().getName(),
-        accountId.get() + "@" + GERRIT_PLACEHOLDER_HOST,
-        when != null ? when : cb.getCommitter().getWhen(),
-        cb.getCommitter().getTimeZone()));
-    if (when != null) {
-      md.getCommitBuilder().setAuthor(new PersonIdent(
-          md.getCommitBuilder().getAuthor(), when));
-    }
+    cb.setCommitter(newCommitter());
     return super.commit(md);
   }
 
+  public PersonIdent newIdent(Account author) {
+    return new PersonIdent(
+        author.getFullName(),
+        author.getId().get() + "@" + GERRIT_PLACEHOLDER_HOST,
+        when, tz);
+  }
+
+  public PersonIdent newCommitter() {
+    return newIdent(account);
+  }
+
   @Override
   protected String getRefName() {
     return ChangeNoteUtil.changeRefName(change.getId());
@@ -168,7 +207,7 @@
 
   @Override
   protected void onSave(CommitBuilder commit) {
-    if (approvals.isEmpty()) {
+    if (approvals.isEmpty() && reviewers.isEmpty()) {
       return;
     }
     int ps = psId != null ? psId.get() : change.currentPatchSetId().get();
@@ -180,6 +219,13 @@
     }
     msg.append("\n\n");
     addFooter(msg, FOOTER_PATCH_SET, ps);
+    for (Map.Entry<Account.Id, ReviewerState> e : reviewers.entrySet()) {
+      Account account = accountCache.get(e.getKey()).getAccount();
+      PersonIdent ident = newIdent(account);
+      addFooter(msg, e.getValue().getFooterKey())
+          .append(ident.getName())
+          .append(" <").append(ident.getEmailAddress()).append(">\n");
+    }
     for (Map.Entry<String, Short> e : approvals.entrySet()) {
       LabelType lt = labelTypes.byLabel(e.getKey());
       if (lt != null) {
@@ -190,9 +236,13 @@
     commit.setMessage(msg.toString());
   }
 
+  private static StringBuilder addFooter(StringBuilder sb, FooterKey footer) {
+    return sb.append(footer.getName()).append(": ");
+  }
+
   private static void addFooter(StringBuilder sb, FooterKey footer,
       Object value) {
-    sb.append(footer.getName()).append(": ").append(value).append('\n');
+    addFooter(sb, footer).append(value).append('\n');
   }
 
   @Override
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ReviewerState.java b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ReviewerState.java
new file mode 100644
index 0000000..b829a69
--- /dev/null
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ReviewerState.java
@@ -0,0 +1,39 @@
+// Copyright (C) 2013 The Android Open Source Project
+//
+// Licensed 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
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// 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 com.google.gerrit.server.notedb;
+
+import org.eclipse.jgit.revwalk.FooterKey;
+
+/** State of a reviewer on a change. */
+public enum ReviewerState {
+  /** The user has contributed at least one nonzero vote on the change. */
+  REVIEWER(new FooterKey("Reviewer")),
+
+  /** The reviewer was added to the change, but has not voted. */
+  CC(new FooterKey("CC")),
+
+  /** The user was previously a reviewer on the change, but was removed. */
+  REMOVED(new FooterKey("Removed"));
+
+  private final FooterKey footerKey;
+
+  private ReviewerState(FooterKey footerKey) {
+    this.footerKey = footerKey;
+  }
+
+  FooterKey getFooterKey() {
+    return footerKey;
+  }
+}
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 376d8c6..b21632a 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
@@ -34,9 +34,9 @@
 import com.google.gerrit.reviewdb.client.PatchSetApproval;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.ApprovalsUtil;
-import com.google.gerrit.server.ApprovalsUtil.ReviewerState;
 import com.google.gerrit.server.CurrentUser;
 import com.google.gerrit.server.git.GitRepositoryManager;
+import com.google.gerrit.server.notedb.ReviewerState;
 import com.google.gerrit.server.patch.PatchList;
 import com.google.gerrit.server.patch.PatchListCache;
 import com.google.gerrit.server.patch.PatchListEntry;
diff --git a/gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeNotesTest.java b/gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeNotesTest.java
index b614921..6d72456 100644
--- a/gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeNotesTest.java
+++ b/gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeNotesTest.java
@@ -16,15 +16,14 @@
 
 import static com.google.gerrit.server.project.Util.category;
 import static com.google.gerrit.server.project.Util.value;
-
 import static java.util.concurrent.TimeUnit.DAYS;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.concurrent.TimeUnit.MINUTES;
 import static java.util.concurrent.TimeUnit.SECONDS;
-
 import static org.junit.Assert.assertEquals;
 
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSetMultimap;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.ListMultimap;
 import com.google.gerrit.common.data.LabelTypes;
@@ -39,6 +38,7 @@
 import com.google.gerrit.server.extensions.events.GitReferenceUpdated;
 import com.google.gerrit.server.git.MetaDataUpdate;
 import com.google.gerrit.server.util.TimeUtil;
+import com.google.gerrit.testutil.FakeAccountCache;
 import com.google.gerrit.testutil.InMemoryRepositoryManager;
 
 import org.eclipse.jgit.errors.ConfigInvalidException;
@@ -63,7 +63,18 @@
   private static final TimeZone TZ =
       TimeZone.getTimeZone("America/Los_Angeles");
 
-  private LabelTypes LABEL_TYPES = new LabelTypes(ImmutableList.of(
+  private static final Account CHANGE_OWNER;
+  private static final Account OTHER_ACCOUNT;
+  static {
+    CHANGE_OWNER = new Account(new Account.Id(1), TimeUtil.nowTs());
+    CHANGE_OWNER.setFullName("Change Owner");
+    CHANGE_OWNER.setPreferredEmail("change@owner.com");
+    OTHER_ACCOUNT = new Account(new Account.Id(2), TimeUtil.nowTs());
+    OTHER_ACCOUNT.setFullName("Other Account");
+    OTHER_ACCOUNT.setPreferredEmail("other@account.com");
+  }
+
+  private static final LabelTypes LABEL_TYPES = new LabelTypes(ImmutableList.of(
       category("Verified",
         value(1, "Verified"),
         value(0, "No score"),
@@ -76,6 +87,7 @@
   private Project.NameKey project;
   private InMemoryRepositoryManager repoManager;
   private InMemoryRepository repo;
+  private FakeAccountCache accountCache;
   private volatile long clockStepMs;
 
   @Before
@@ -83,6 +95,9 @@
     project = new Project.NameKey("test-project");
     repoManager = new InMemoryRepositoryManager();
     repo = repoManager.createRepository(project);
+    accountCache = new FakeAccountCache();
+    accountCache.put(CHANGE_OWNER);
+    accountCache.put(OTHER_ACCOUNT);
   }
 
   @Before
@@ -107,10 +122,12 @@
 
   @Test
   public void approvalsCommitFormat() throws Exception {
-    Change c = newChange(5);
-    ChangeUpdate update = newUpdate(c, c.getOwner());
+    Change c = newChange();
+    ChangeUpdate update = newUpdate(c, CHANGE_OWNER);
     update.putApproval("Code-Review", (short) -1);
     update.putApproval("Verified", (short) 1);
+    update.putReviewer(CHANGE_OWNER.getId(), ReviewerState.REVIEWER);
+    update.putReviewer(OTHER_ACCOUNT.getId(), ReviewerState.CC);
     commit(update);
     assertEquals("refs/changes/01/1/meta", update.getRefName());
 
@@ -121,20 +138,22 @@
       assertEquals("Update patch set 1\n"
           + "\n"
           + "Patch-Set: 1\n"
+          + "Reviewer: Change Owner <1@gerrit>\n"
+          + "CC: Other Account <2@gerrit>\n"
           + "Label: Verified=+1\n"
           + "Label: Code-Review=-1\n",
           commit.getFullMessage());
 
       PersonIdent author = commit.getAuthorIdent();
-      assertEquals("Example User", author.getName());
-      assertEquals("user@example.com", author.getEmailAddress());
+      assertEquals("Change Owner", author.getName());
+      assertEquals("change@owner.com", author.getEmailAddress());
       assertEquals(new Date(c.getCreatedOn().getTime() + 1000),
           author.getWhen());
       assertEquals(TimeZone.getTimeZone("GMT-8:00"), author.getTimeZone());
 
       PersonIdent committer = commit.getCommitterIdent();
-      assertEquals("Example User", committer.getName());
-      assertEquals("5@gerrit", committer.getEmailAddress());
+      assertEquals("Change Owner", committer.getName());
+      assertEquals("1@gerrit", committer.getEmailAddress());
       assertEquals(author.getWhen(), committer.getWhen());
       assertEquals(author.getTimeZone(), committer.getTimeZone());
     } finally {
@@ -144,8 +163,8 @@
 
   @Test
   public void approvalsOnePatchSet() throws Exception {
-    Change c = newChange(5);
-    ChangeUpdate update = newUpdate(c, c.getOwner());
+    Change c = newChange();
+    ChangeUpdate update = newUpdate(c, CHANGE_OWNER);
     update.putApproval("Code-Review", (short) -1);
     update.putApproval("Verified", (short) 1);
     commit(update);
@@ -157,13 +176,13 @@
     assertEquals(2, psas.size());
 
     assertEquals(c.currentPatchSetId(), psas.get(0).getPatchSetId());
-    assertEquals(5, psas.get(0).getAccountId().get());
+    assertEquals(1, psas.get(0).getAccountId().get());
     assertEquals("Verified", psas.get(0).getLabel());
     assertEquals((short) 1, psas.get(0).getValue());
     assertEquals(truncate(after(c, 1000)), psas.get(0).getGranted());
 
     assertEquals(c.currentPatchSetId(), psas.get(1).getPatchSetId());
-    assertEquals(5, psas.get(1).getAccountId().get());
+    assertEquals(1, psas.get(1).getAccountId().get());
     assertEquals("Code-Review", psas.get(1).getLabel());
     assertEquals((short) -1, psas.get(1).getValue());
     assertEquals(psas.get(0).getGranted(), psas.get(1).getGranted());
@@ -171,14 +190,14 @@
 
   @Test
   public void approvalsMultiplePatchSets() throws Exception {
-    Change c = newChange(5);
-    ChangeUpdate update = newUpdate(c, c.getOwner());
+    Change c = newChange();
+    ChangeUpdate update = newUpdate(c, CHANGE_OWNER);
     update.putApproval("Code-Review", (short) -1);
     commit(update);
     PatchSet.Id ps1 = c.currentPatchSetId();
 
     incrementPatchSet(c);
-    update = newUpdate(c, c.getOwner());
+    update = newUpdate(c, CHANGE_OWNER);
     update.putApproval("Code-Review", (short) 1);
     commit(update);
     PatchSet.Id ps2 = c.currentPatchSetId();
@@ -189,14 +208,14 @@
 
     PatchSetApproval psa1 = Iterables.getOnlyElement(psas.get(ps1));
     assertEquals(ps1, psa1.getPatchSetId());
-    assertEquals(5, psa1.getAccountId().get());
+    assertEquals(1, psa1.getAccountId().get());
     assertEquals("Code-Review", psa1.getLabel());
     assertEquals((short) -1, psa1.getValue());
     assertEquals(truncate(after(c, 1000)), psa1.getGranted());
 
     PatchSetApproval psa2 = Iterables.getOnlyElement(psas.get(ps2));
     assertEquals(ps2, psa2.getPatchSetId());
-    assertEquals(5, psa2.getAccountId().get());
+    assertEquals(1, psa2.getAccountId().get());
     assertEquals("Code-Review", psa2.getLabel());
     assertEquals((short) +1, psa2.getValue());
     assertEquals(truncate(after(c, 2000)), psa2.getGranted());
@@ -204,8 +223,8 @@
 
   @Test
   public void approvalsMultipleApprovals() throws Exception {
-    Change c = newChange(5);
-    ChangeUpdate update = newUpdate(c, c.getOwner());
+    Change c = newChange();
+    ChangeUpdate update = newUpdate(c, CHANGE_OWNER);
     update.putApproval("Code-Review", (short) -1);
     commit(update);
 
@@ -215,7 +234,7 @@
     assertEquals("Code-Review", psa.getLabel());
     assertEquals((short) -1, psa.getValue());
 
-    update = newUpdate(c, c.getOwner());
+    update = newUpdate(c, CHANGE_OWNER);
     update.putApproval("Code-Review", (short) 1);
     commit(update);
 
@@ -228,12 +247,12 @@
 
   @Test
   public void approvalsMultipleUsers() throws Exception {
-    Change c = newChange(5);
-    ChangeUpdate update = newUpdate(c, c.getOwner());
+    Change c = newChange();
+    ChangeUpdate update = newUpdate(c, CHANGE_OWNER);
     update.putApproval("Code-Review", (short) -1);
     commit(update);
 
-    update = newUpdate(c, new Account.Id(6));
+    update = newUpdate(c, OTHER_ACCOUNT);
     update.putApproval("Code-Review", (short) 1);
     commit(update);
 
@@ -244,33 +263,118 @@
     assertEquals(2, psas.size());
 
     assertEquals(c.currentPatchSetId(), psas.get(0).getPatchSetId());
-    assertEquals(5, psas.get(0).getAccountId().get());
+    assertEquals(1, psas.get(0).getAccountId().get());
     assertEquals("Code-Review", psas.get(0).getLabel());
     assertEquals((short) -1, psas.get(0).getValue());
     assertEquals(truncate(after(c, 1000)), psas.get(0).getGranted());
 
     assertEquals(c.currentPatchSetId(), psas.get(1).getPatchSetId());
-    assertEquals(6, psas.get(1).getAccountId().get());
+    assertEquals(2, psas.get(1).getAccountId().get());
     assertEquals("Code-Review", psas.get(1).getLabel());
     assertEquals((short) 1, psas.get(1).getValue());
     assertEquals(truncate(after(c, 2000)), psas.get(1).getGranted());
   }
 
-  private Change newChange(int accountId) {
+  @Test
+  public void multipleReviewers() throws Exception {
+    Change c = newChange();
+    ChangeUpdate update = newUpdate(c, CHANGE_OWNER);
+    update.putReviewer(CHANGE_OWNER.getId(), ReviewerState.REVIEWER);
+    update.putReviewer(OTHER_ACCOUNT.getId(), ReviewerState.REVIEWER);
+    commit(update);
+
+    ChangeNotes notes = newNotes(c);
+    assertEquals(ImmutableSetMultimap.of(
+          ReviewerState.REVIEWER, new Account.Id(1),
+          ReviewerState.REVIEWER, new Account.Id(2)),
+        notes.getReviewers());
+  }
+
+  @Test
+  public void reviewerTypes() throws Exception {
+    Change c = newChange();
+    ChangeUpdate update = newUpdate(c, CHANGE_OWNER);
+    update.putReviewer(CHANGE_OWNER.getId(), ReviewerState.REVIEWER);
+    update.putReviewer(OTHER_ACCOUNT.getId(), ReviewerState.CC);
+    commit(update);
+
+    ChangeNotes notes = newNotes(c);
+    assertEquals(ImmutableSetMultimap.of(
+          ReviewerState.REVIEWER, new Account.Id(1),
+          ReviewerState.CC, new Account.Id(2)),
+        notes.getReviewers());
+  }
+
+  @Test
+  public void oneReviewerMultipleTypes() throws Exception {
+    Change c = newChange();
+    ChangeUpdate update = newUpdate(c, CHANGE_OWNER);
+    update.putReviewer(OTHER_ACCOUNT.getId(), ReviewerState.REVIEWER);
+    commit(update);
+
+    ChangeNotes notes = newNotes(c);
+    assertEquals(ImmutableSetMultimap.of(
+          ReviewerState.REVIEWER, new Account.Id(2)),
+        notes.getReviewers());
+
+    update = newUpdate(c, OTHER_ACCOUNT);
+    update.putReviewer(OTHER_ACCOUNT.getId(), ReviewerState.CC);
+    commit(update);
+
+    notes = newNotes(c);
+    assertEquals(ImmutableSetMultimap.of(
+          ReviewerState.CC, new Account.Id(2)),
+        notes.getReviewers());
+  }
+
+  @Test
+  public void removeReviewer() throws Exception {
+    Change c = newChange();
+    ChangeUpdate update = newUpdate(c, CHANGE_OWNER);
+    update.putReviewer(OTHER_ACCOUNT.getId(), ReviewerState.REVIEWER);
+    commit(update);
+
+    update = newUpdate(c, CHANGE_OWNER);
+    update.putApproval("Code-Review", (short) 1);
+    commit(update);
+
+    update = newUpdate(c, OTHER_ACCOUNT);
+    update.putApproval("Code-Review", (short) 1);
+    commit(update);
+
+    ChangeNotes notes = newNotes(c);
+    List<PatchSetApproval> psas =
+        notes.getApprovals().get(c.currentPatchSetId());
+    assertEquals(2, psas.size());
+    assertEquals(CHANGE_OWNER.getId(), psas.get(0).getAccountId());
+    assertEquals(OTHER_ACCOUNT.getId(), psas.get(1).getAccountId());
+
+    update = newUpdate(c, CHANGE_OWNER);
+    update.removeReviewer(OTHER_ACCOUNT.getId());
+    commit(update);
+
+    notes = newNotes(c);
+    psas = notes.getApprovals().get(c.currentPatchSetId());
+    assertEquals(1, psas.size());
+    assertEquals(CHANGE_OWNER.getId(), psas.get(0).getAccountId());
+  }
+
+  private Change newChange() {
     Change.Id changeId = new Change.Id(1);
     Change c = new Change(
         new Change.Key("Iabcd1234abcd1234abcd1234abcd1234abcd1234"),
         changeId,
-        new Account.Id(accountId),
+        CHANGE_OWNER.getId(),
         new Branch.NameKey(project, "master"),
         TimeUtil.nowTs());
     incrementPatchSet(c);
     return c;
   }
 
-  private ChangeUpdate newUpdate(Change c, Account.Id owner)
+  private ChangeUpdate newUpdate(Change c, Account account)
       throws ConfigInvalidException, IOException {
-    return new ChangeUpdate(repoManager, LABEL_TYPES, c, owner, null);
+    return new ChangeUpdate(repoManager, accountCache, LABEL_TYPES, c, account,
+        TimeUtil.nowTs(), TZ);
   }
 
   private ChangeNotes newNotes(Change c)
@@ -297,11 +401,10 @@
   private RevCommit commit(ChangeUpdate update) throws IOException {
     MetaDataUpdate md = new MetaDataUpdate(GitReferenceUpdated.DISABLED,
         project, repo);
-    Timestamp ts = TimeUtil.nowTs();
-    md.getCommitBuilder().setAuthor(
-        new PersonIdent("Example User", "user@example.com", ts, TZ));
-    md.getCommitBuilder().setCommitter(
-        new PersonIdent("Gerrit Test", "notthis@email.com", ts, TZ));
+    md.getCommitBuilder().setAuthor(new PersonIdent(
+        update.getAccount().getFullName(),
+        update.getAccount().getPreferredEmail(),
+        update.getWhen(), TZ));
     return update.commit(md);
   }
 }
diff --git a/gerrit-server/src/test/java/com/google/gerrit/testutil/FakeAccountCache.java b/gerrit-server/src/test/java/com/google/gerrit/testutil/FakeAccountCache.java
new file mode 100644
index 0000000..db1ed05
--- /dev/null
+++ b/gerrit-server/src/test/java/com/google/gerrit/testutil/FakeAccountCache.java
@@ -0,0 +1,80 @@
+// Copyright (C) 2013 The Android Open Source Project
+//
+// Licensed 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
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// 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 com.google.gerrit.testutil;
+
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Maps;
+import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.reviewdb.client.AccountExternalId;
+import com.google.gerrit.reviewdb.client.AccountGroup;
+import com.google.gerrit.server.account.AccountCache;
+import com.google.gerrit.server.account.AccountState;
+import com.google.gerrit.server.util.TimeUtil;
+
+import java.util.Map;
+
+/** Fake implementation of {@link AccountCache} for testing. */
+public class FakeAccountCache implements AccountCache {
+  private final Map<Account.Id, AccountState> byId;
+  private final Map<String, AccountState> byUsername;
+
+  public FakeAccountCache() {
+    byId = Maps.newHashMap();
+    byUsername = Maps.newHashMap();
+  }
+
+  @Override
+  public synchronized AccountState get(Account.Id accountId) {
+    AccountState state = getIfPresent(accountId);
+    if (state != null) {
+      return state;
+    }
+    return newState(new Account(accountId, TimeUtil.nowTs()));
+  }
+
+  @Override
+  public synchronized AccountState getIfPresent(Account.Id accountId) {
+    return byId.get(accountId);
+  }
+
+  @Override
+  public synchronized AccountState getByUsername(String username) {
+    return byUsername.get(username);
+  }
+
+  @Override
+  public synchronized void evict(Account.Id accountId) {
+    byId.remove(accountId);
+  }
+
+  @Override
+  public synchronized void evictByUsername(String username) {
+    byUsername.remove(username);
+  }
+
+  public synchronized void put(Account account) {
+    AccountState state = newState(account);
+    byId.put(account.getId(), state);
+    if (account.getUserName() != null) {
+      byUsername.put(account.getUserName(), state);
+    }
+  }
+
+  private static AccountState newState(Account account) {
+    return new AccountState(
+        account, ImmutableSet.<AccountGroup.UUID> of(),
+        ImmutableSet.<AccountExternalId> of());
+  }
+}