diff --git a/core/lib/Drupal/Core/KeyValueStore/DatabaseStorageExpirable.php b/core/lib/Drupal/Core/KeyValueStore/DatabaseStorageExpirable.php
index 58785c4..1bcbe47 100644
--- a/core/lib/Drupal/Core/KeyValueStore/DatabaseStorageExpirable.php
+++ b/core/lib/Drupal/Core/KeyValueStore/DatabaseStorageExpirable.php
@@ -8,6 +8,7 @@
 namespace Drupal\Core\KeyValueStore;
 
 use Drupal\Core\Database\Query\Merge;
+use Drupal\Core\Database\Database;
 
 /**
  * Defines a default key/value store implementation for expiring items.
@@ -32,13 +33,14 @@ class DatabaseStorageExpirable extends DatabaseStorage implements KeyValueStoreE
    * @param array $options
    *   An associative array of options for the key/value storage collection.
    *   Keys used:
-   *   - connection: The database connection to use for storing the data.
+   *   - connection: (optional) The database connection to use for storing the
+   *     data. Defaults to the current connection.
    *   - table: (optional) The name of the SQL table to use. Defaults to
    *     key_value_expire.
    */
   public function __construct($collection, array $options = array()) {
     parent::__construct($collection, $options);
-    $this->connection = $options['connection'];
+    $this->connection = isset($options['connection']) ? $options['connection'] : Database::getConnection();
     $this->table = isset($options['table']) ? $options['table'] : 'key_value_expire';
   }
 
@@ -46,41 +48,27 @@ public function __construct($collection, array $options = array()) {
    * Implements Drupal\Core\KeyValueStore\KeyValueStoreInterface::getMultiple().
    */
   public function getMultiple(array $keys) {
-    $values = array();
-    try {
-      $result = $this->connection->query('SELECT name, value, expire FROM {' . $this->connection->escapeTable($this->table) . '} WHERE expire > :now AND name IN (:keys) AND collection = :collection',
-        array(
-          ':now' => REQUEST_TIME,
-          ':keys' => $keys,
-          ':collection' => $this->collection,
-      ))->fetchAllAssoc('name');
-      foreach ($keys as $key) {
-        if (isset($result[$key])) {
-          $values[$key] = unserialize($result[$key]->value);
-        }
-      }
-    }
-    catch (\Exception $e) {
-      // @todo Perhaps if the database is never going to be available,
-      //   key/value requests should return FALSE in order to allow exception
-      //   handling to occur but for now, keep it an array, always.
-    }
-    return $values;
+    $values = $this->connection->query(
+      'SELECT name, value FROM {' . $this->connection->escapeTable($this->table) . '} WHERE expire > :now AND name IN (:keys) AND collection = :collection',
+      array(
+        ':now' => REQUEST_TIME,
+        ':keys' => $keys,
+        ':collection' => $this->collection,
+      ))->fetchAllKeyed();
+    return array_map('unserialize', $values);
   }
 
   /**
    * Implements Drupal\Core\KeyValueStore\KeyValueStoreInterface::getAll().
    */
   public function getAll() {
-    $result = $this->connection->query('SELECT name, value FROM {' . $this->connection->escapeTable($this->table) . '} WHERE collection = :collection AND expire > :now', array(':collection' => $this->collection, ':now' => REQUEST_TIME));
-    $values = array();
-
-    foreach ($result as $item) {
-      if ($item) {
-        $values[$item->name] = unserialize($item->value);
-      }
-    }
-    return $values;
+    $values = $this->connection->query(
+      'SELECT name, value FROM {' . $this->connection->escapeTable($this->table) . '} WHERE collection = :collection AND expire > :now',
+      array(
+        ':collection' => $this->collection,
+        ':now' => REQUEST_TIME
+      ))->fetchAllKeyed();
+    return array_map('unserialize', $values);
   }
 
   /**
diff --git a/core/modules/system/lib/Drupal/system/Tests/KeyValueStore/DatabaseStorageExpirableTest.php b/core/modules/system/lib/Drupal/system/Tests/KeyValueStore/DatabaseStorageExpirableTest.php
new file mode 100644
index 0000000..db85d35
--- /dev/null
+++ b/core/modules/system/lib/Drupal/system/Tests/KeyValueStore/DatabaseStorageExpirableTest.php
@@ -0,0 +1,42 @@
+<?php
+
+/**
+ * @file
+ * Contains Drupal\system\Tests\KeyValueStore\DatabaseStorageExpirableTest.
+ */
+
+namespace Drupal\system\Tests\KeyValueStore;
+
+/**
+ * Tests the key-value database storage.
+ */
+class DatabaseStorageExpirableTest extends StorageTestBase {
+
+  /**
+   * The name of the class to test.
+   *
+   * The tests themselves are in StorageTestBase and use this class.
+   */
+  protected $storageClass = 'Drupal\Core\KeyValueStore\DatabaseStorageExpirable';
+
+  public static function getInfo() {
+    return array(
+      'name' => 'Expirable database storage',
+      'description' => 'Tests the expirable key-value database storage.',
+      'group' => 'Key-value store',
+    );
+  }
+
+  protected function setUp() {
+    parent::setUp();
+    module_load_install('system');
+    $schema = system_schema();
+    db_create_table('key_value_expire', $schema['key_value_expire']);
+  }
+
+  protected function tearDown() {
+    db_drop_table('key_value_expire');
+    parent::tearDown();
+  }
+
+}
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index a177b3e..3382fdf 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -858,10 +858,10 @@ function system_schema() {
         'translatable' => TRUE,
       ),
       'expire' => array(
-        'description' => 'The time since Unix epoch in seconds when this item expires.',
+        'description' => 'The time since Unix epoch in seconds when this item expires. Defaults to January 18 2038 (the end of the Unix epoch).',
         'type' => 'int',
         'not null' => TRUE,
-        'default' => 0,
+        'default' => 2147483647,
       ),
     ),
     'primary key' => array('collection', 'name'),
@@ -2172,7 +2172,7 @@ function system_update_8023() {
         'description' => 'The time since Unix epoch in seconds when this item expires.',
         'type' => 'int',
         'not null' => TRUE,
-        'default' => 0,
+        'default' => 2147483647,
       ),
     ),
     'primary key' => array('collection', 'name'),
diff --git a/core/modules/user/lib/Drupal/user/TempStore.php b/core/modules/user/lib/Drupal/user/TempStore.php
index 58f0495..3ee8732 100644
--- a/core/modules/user/lib/Drupal/user/TempStore.php
+++ b/core/modules/user/lib/Drupal/user/TempStore.php
@@ -119,9 +119,6 @@ function setIfNotExists($key, $value) {
    *   The key of the data to store.
    * @param mixed $value
    *   The data to store.
-   *
-   * @todo Should we throw an exception here if the lock cannot be acquired
-   *   like we do in delete()?
    */
   function set($key, $value) {
     if (!$this->lockBackend->acquire($key)) {