diff --git a/core/lib/Drupal/Core/Cache/DatabaseBackend.php b/core/lib/Drupal/Core/Cache/DatabaseBackend.php
index 4c431dc..8221aee 100644
--- a/core/lib/Drupal/Core/Cache/DatabaseBackend.php
+++ b/core/lib/Drupal/Core/Cache/DatabaseBackend.php
@@ -62,6 +62,10 @@ public function get($cid, $allow_invalid = FALSE) {
    * Implements Drupal\Core\Cache\CacheBackendInterface::getMultiple().
    */
   public function getMultiple(&$cids, $allow_invalid = FALSE) {
+    $cid_mapping = array();
+    foreach ($cids as $cid) {
+      $cid_mapping[$this->ensureCidLength($cid)] = $cid;
+    }
     // When serving cached pages, the overhead of using ::select() was found
     // to add around 30% overhead to the request. Since $this->bin is a
     // variable, this means the call to ::query() here uses a concatenated
@@ -71,13 +75,15 @@ public function getMultiple(&$cids, $allow_invalid = FALSE) {
     // ::select() is a much smaller proportion of the request.
     $result = array();
     try {
-      $result = $this->connection->query('SELECT cid, data, created, expire, serialized, tags, checksum_invalidations, checksum_deletions FROM {' . $this->connection->escapeTable($this->bin) . '} WHERE cid IN (:cids)', array(':cids' => $cids));
+      $result = $this->connection->query('SELECT cid, data, created, expire, serialized, tags, checksum_invalidations, checksum_deletions FROM {' . $this->connection->escapeTable($this->bin) . '} WHERE cid IN (:cids)', array(':cids' => array_keys($cid_mapping)));
     }
     catch (\Exception $e) {
       // Nothing to do.
     }
     $cache = array();
     foreach ($result as $item) {
+      // Map the cache ID back to the original.
+      $item->cid = $cid_mapping[$item->cid];
       $item = $this->prepareItem($item, $allow_invalid);
       if ($item) {
         $cache[$item->cid] = $item;
@@ -196,7 +202,7 @@ protected function doSet($cid, $data, $expire, $tags) {
     }
 
     $this->connection->merge($this->bin)
-      ->key('cid', $cid)
+      ->key('cid', $this->ensureCidLength($cid))
       ->fields($fields)
       ->execute();
   }
@@ -212,6 +218,7 @@ public function delete($cid) {
    * Implements Drupal\Core\Cache\CacheBackendInterface::deleteMultiple().
    */
   public function deleteMultiple(array $cids) {
+    $cids = array_values(array_map(array($this, 'ensureCidLength'), $cids));
     try {
       // Delete in chunks when a large array is passed.
       do {
@@ -285,6 +292,7 @@ public function invalidate($cid) {
    * Implements Drupal\Core\Cache\CacheBackendInterface::invalideMultiple().
    */
   public function invalidateMultiple(array $cids) {
+    $cids = array_values(array_map(array($this, 'ensureCidLength'), $cids));
     try {
       // Update in chunks when a large array is passed.
       do {
@@ -495,6 +503,26 @@ protected function catchException(\Exception $e, $table_name = NULL) {
   }
 
   /**
+   * Ensures that cache IDs are valid.
+   *
+   * @param string $cid
+   *   The passed in cache ID.
+   *
+   * @return string
+   *   A cache ID that is at most 255 characters long.
+   */
+  protected function ensureCidLength($cid) {
+    // Nothing to do if the ID length is 255 characters or less.
+    if (strlen($cid) <= 255) {
+      return $cid;
+    }
+    // Return a string that uses as much as possible of the original cache ID
+    // with the hash appended.
+    $hash = hash('sha1', $cid);
+    return substr($cid, 0, 255 - strlen($hash)) . $hash;
+  }
+
+  /**
    * Defines the schema for the cache bin and cache_tags table.
    */
   public function schemaDefinition() {
diff --git a/core/modules/system/lib/Drupal/system/Tests/Cache/GenericCacheBackendUnitTestBase.php b/core/modules/system/lib/Drupal/system/Tests/Cache/GenericCacheBackendUnitTestBase.php
index e558816..e3f610b 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Cache/GenericCacheBackendUnitTestBase.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Cache/GenericCacheBackendUnitTestBase.php
@@ -159,6 +159,11 @@ public function testSetGet() {
     $this->assertFalse($cached->valid, 'Item is marked as valid.');
     $this->assertEqual($cached->created, REQUEST_TIME, 'Created time is correct.');
     $this->assertEqual($cached->expire, REQUEST_TIME - 3, 'Expire time is correct.');
+
+    // Check with a long key.
+    $cid = str_repeat('a', 300);
+    $backend->set($cid, 'test');
+    $this->assertEqual('test', $backend->get($cid)->data);
   }
 
   /**
@@ -182,6 +187,11 @@ public function testDelete() {
 
     $backend->delete('test2');
     $this->assertIdentical(FALSE, $backend->get('test2'), "Backend does not contain data for cache id test2 after deletion.");
+
+    $long_cid = str_repeat('a', 300);
+    $backend->set($long_cid, 'test');
+    $backend->delete($long_cid);
+    $this->assertIdentical(FALSE, $backend->get($long_cid), "Backend does not contain data for long cache id after deletion.");
   }
 
   /**
@@ -219,6 +229,7 @@ public function testGetMultiple() {
     $backend = $this->getCacheBackend();
 
     // Set numerous testing keys.
+    $long_cid = str_repeat('a', 300);
     $backend->set('test1', 1);
     $backend->set('test2', 3);
     $backend->set('test3', 5);
@@ -226,6 +237,7 @@ public function testGetMultiple() {
     $backend->set('test5', 11);
     $backend->set('test6', 13);
     $backend->set('test7', 17);
+    $backend->set($long_cid, 300);
 
     // Mismatch order for harder testing.
     $reference = array(
@@ -293,6 +305,11 @@ public function testGetMultiple() {
     $this->assertFalse(in_array('test2', $cids), "Existing cache id test2 is not in cids array.");
     $this->assertFalse(in_array('test7', $cids), "Existing cache id test7 is not in cids array.");
     $this->assertFalse(in_array('test19', $cids), "Added cache id test19 is not in cids array.");
+    // Test with a long $cid and non-numeric array key.
+    $cids = array('key:key' => $long_cid);
+    $return = $backend->getMultiple($cids);
+    $this->assertEqual(300, $return[$long_cid]->data);
+    $this->assertTrue(empty($cids));
   }
 
   /**