diff --git a/java/com/google/gerrit/server/change/ChangeFinder.java b/java/com/google/gerrit/server/change/ChangeFinder.java
index 71d7ba0..ba104d8 100644
--- a/java/com/google/gerrit/server/change/ChangeFinder.java
+++ b/java/com/google/gerrit/server/change/ChangeFinder.java
@@ -100,7 +100,9 @@
   }
 
   public Optional<ChangeNotes> findOne(String id) {
-    List<ChangeNotes> ctls = find(id);
+    // Limit the maximum number of results to just 2 items for saving CPU cycles
+    // in reading change-notes.
+    List<ChangeNotes> ctls = find(id, 2);
     if (ctls.size() != 1) {
       return Optional.empty();
     }
@@ -114,6 +116,17 @@
    * @return possibly-empty list of notes for all matching changes; may or may not be visible.
    */
   public List<ChangeNotes> find(String id) {
+    return find(id, 0);
+  }
+
+  /**
+   * Find at most N changes matching the given identifier.
+   *
+   * @param id change identifier.
+   * @param queryLimit maximum number of changes to be returned
+   * @return possibly-empty list of notes for all matching changes; may or may not be visible.
+   */
+  public List<ChangeNotes> find(String id, int queryLimit) {
     if (id.isEmpty()) {
       return Collections.emptyList();
     }
@@ -141,6 +154,9 @@
     // Use the index to search for changes, but don't return any stored fields,
     // to force rereading in case the index is stale.
     InternalChangeQuery query = queryProvider.get().noFields();
+    if (queryLimit > 0) {
+      query.setLimit(queryLimit);
+    }
 
     // Try commit hash
     if (id.matches("^([0-9a-fA-F]{" + ObjectIds.ABBREV_STR_LEN + "," + ObjectIds.STR_LEN + "})$")) {
diff --git a/java/com/google/gerrit/server/restapi/change/ChangesCollection.java b/java/com/google/gerrit/server/restapi/change/ChangesCollection.java
index 95b74f8..572f704 100644
--- a/java/com/google/gerrit/server/restapi/change/ChangesCollection.java
+++ b/java/com/google/gerrit/server/restapi/change/ChangesCollection.java
@@ -82,7 +82,7 @@
   @Override
   public ChangeResource parse(TopLevelResource root, IdString id)
       throws RestApiException, PermissionBackendException, IOException {
-    List<ChangeNotes> notes = changeFinder.find(id.encoded());
+    List<ChangeNotes> notes = changeFinder.find(id.encoded(), 2);
     if (notes.isEmpty()) {
       throw new ResourceNotFoundException(id);
     } else if (notes.size() != 1) {
diff --git a/javatests/com/google/gerrit/acceptance/rest/change/ChangeIdIT.java b/javatests/com/google/gerrit/acceptance/rest/change/ChangeIdIT.java
index bc52681..06e24ab 100644
--- a/javatests/com/google/gerrit/acceptance/rest/change/ChangeIdIT.java
+++ b/javatests/com/google/gerrit/acceptance/rest/change/ChangeIdIT.java
@@ -81,6 +81,14 @@
   }
 
   @Test
+  public void tripletWithoutChangeIdReturnsNotFound() throws Exception {
+    createChange().assertOkStatus();
+    createChange().assertOkStatus();
+    RestResponse res = adminRestSession.get(changeDetail(project.get() + "~master~"));
+    res.assertNotFound();
+  }
+
+  @Test
   public void changeIdReturnsChange() throws Exception {
     PushOneCommit.Result c = createChange();
     RestResponse res = adminRestSession.get(changeDetail(c.getChangeId()));