diff --git a/core/lib/Drupal/Core/Path/AliasStorage.php b/core/lib/Drupal/Core/Path/AliasStorage.php
index 0ef4a12..4385923 100644
--- a/core/lib/Drupal/Core/Path/AliasStorage.php
+++ b/core/lib/Drupal/Core/Path/AliasStorage.php
@@ -60,7 +60,7 @@ public function save($source, $alias, $langcode = LanguageInterface::LANGCODE_NO
 
     $fields = array(
       'source' => $source,
-      'alias' => Unicode::strtolower($alias),
+      'alias' => $alias,
       'langcode' => $langcode,
     );
 
@@ -132,7 +132,6 @@ public function delete($conditions) {
    */
   public function preloadPathAlias($preloaded, $langcode) {
     $args = array(
-      ':system[]' => $preloaded,
       ':langcode' => $langcode,
       ':langcode_undetermined' => LanguageInterface::LANGCODE_NOT_SPECIFIED,
     );
@@ -143,19 +142,22 @@ public function preloadPathAlias($preloaded, $langcode) {
     // created alias for each source. Subsequent queries using fetchField() must
     // use pid DESC to have the same effect. For performance reasons, the query
     // builder is not used here.
+    $select = $this->connection->select('url_alias');
+    $select->fields('url_alias', ['source', 'alias']);
+    $select->condition('source', $preloaded, 'IN');
     if ($langcode == LanguageInterface::LANGCODE_NOT_SPECIFIED) {
-      // Prevent PDO from complaining about a token the query doesn't use.
+      // Don't put the same value in the IN query twice.
       unset($args[':langcode']);
-      $result = $this->connection->query('SELECT source, alias FROM {url_alias} WHERE source IN ( :system[] ) AND langcode = :langcode_undetermined ORDER BY pid ASC', $args);
     }
     elseif ($langcode < LanguageInterface::LANGCODE_NOT_SPECIFIED) {
-      $result = $this->connection->query('SELECT source, alias FROM {url_alias} WHERE source IN ( :system[] ) AND langcode IN (:langcode, :langcode_undetermined) ORDER BY langcode ASC, pid ASC', $args);
+      $select->orderBy('langcode', 'ASC');
     }
     else {
-      $result = $this->connection->query('SELECT source, alias FROM {url_alias} WHERE source IN ( :system[] ) AND langcode IN (:langcode, :langcode_undetermined) ORDER BY langcode DESC, pid ASC', $args);
+      $select->orderBy('langcode', 'DESC');
     }
-
-    return $result->fetchAllKeyed();
+    $select->condition('langcode', $args, 'IN');
+    $select->orderBy('pid', 'ASC');
+    return $select->execute()->fetchAllKeyed();
   }
 
   /**
@@ -163,23 +165,26 @@ public function preloadPathAlias($preloaded, $langcode) {
    */
   public function lookupPathAlias($path, $langcode) {
     $args = array(
-      ':source' => $path,
       ':langcode' => $langcode,
       ':langcode_undetermined' => LanguageInterface::LANGCODE_NOT_SPECIFIED,
     );
     // See the queries above.
+    $select = $this->connection->select('url_alias');
+    $select->fields('url_alias', ['alias']);
     if ($langcode == LanguageInterface::LANGCODE_NOT_SPECIFIED) {
       unset($args[':langcode']);
-      $alias = $this->connection->query("SELECT alias FROM {url_alias} WHERE source = :source AND langcode = :langcode_undetermined ORDER BY pid DESC", $args)->fetchField();
     }
     elseif ($langcode > LanguageInterface::LANGCODE_NOT_SPECIFIED) {
-      $alias = $this->connection->query("SELECT alias FROM {url_alias} WHERE source = :source AND langcode IN (:langcode, :langcode_undetermined) ORDER BY langcode DESC, pid DESC", $args)->fetchField();
+      $select->orderBy('langcode', 'DESC');
     }
     else {
-      $alias = $this->connection->query("SELECT alias FROM {url_alias} WHERE source = :source AND langcode IN (:langcode, :langcode_undetermined) ORDER BY langcode ASC, pid DESC", $args)->fetchField();
+      $select->orderBy('langcode', 'ASC');
     }
-
-    return $alias;
+    // Use LIKE for case-insensitive matching.
+    $select->condition('source', $path, 'LIKE');
+    $select->condition('langcode', $args, 'IN');
+    $select->orderBy('pid', 'DESC');
+    return $select->execute()->fetchField();
   }
 
   /**
@@ -187,23 +192,26 @@ public function lookupPathAlias($path, $langcode) {
    */
   public function lookupPathSource($path, $langcode) {
     $args = array(
-      ':alias' => Unicode::strtolower($path),
       ':langcode' => $langcode,
       ':langcode_undetermined' => LanguageInterface::LANGCODE_NOT_SPECIFIED,
     );
     // See the queries above.
+    $select = $this->connection->select('url_alias');
+    $select->fields('url_alias', ['source']);
     if ($langcode == LanguageInterface::LANGCODE_NOT_SPECIFIED) {
       unset($args[':langcode']);
-      $result = $this->connection->query("SELECT source FROM {url_alias} WHERE alias = :alias AND langcode = :langcode_undetermined ORDER BY pid DESC", $args);
     }
     elseif ($langcode > LanguageInterface::LANGCODE_NOT_SPECIFIED) {
-      $result = $this->connection->query("SELECT source FROM {url_alias} WHERE alias = :alias AND langcode IN (:langcode, :langcode_undetermined) ORDER BY langcode DESC, pid DESC", $args);
+      $select->orderBy('langcode', 'DESC');
     }
     else {
-      $result = $this->connection->query("SELECT source FROM {url_alias} WHERE alias = :alias AND langcode IN (:langcode, :langcode_undetermined) ORDER BY langcode ASC, pid DESC", $args);
+      $select->orderBy('langcode', 'ASC');
     }
-
-    return $result->fetchField();
+    // Use LIKE for case-insensitive matching.
+    $select->condition('alias', $path, 'LIKE');
+    $select->condition('langcode', $args, 'IN');
+    $select->orderBy('pid', 'DESC');
+    return $select->execute()->fetchField();
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Path/AliasStorageInterface.php b/core/lib/Drupal/Core/Path/AliasStorageInterface.php
index 3f55413..7717aef 100644
--- a/core/lib/Drupal/Core/Path/AliasStorageInterface.php
+++ b/core/lib/Drupal/Core/Path/AliasStorageInterface.php
@@ -20,7 +20,7 @@
    * @param string $source
    *   The internal system path.
    * @param string $alias
-   *   The URL alias. This will be converted to lowercase.
+   *   The URL alias.
    * @param string $langcode
    *   (optional) The language code of the alias.
    * @param int|null $pid
diff --git a/core/modules/system/system.post_update.php b/core/modules/system/system.post_update.php
index b8d089d..b75625c 100644
--- a/core/modules/system/system.post_update.php
+++ b/core/modules/system/system.post_update.php
@@ -39,37 +39,5 @@ function system_post_update_recalculate_configuration_entity_dependencies(&$sand
 }
 
 /**
- * Load and save all path aliases to make sure they are lower case.
- */
-function system_post_update_path_alias_lowercase(&$sandbox = NULL) {
-  // The path alias storage interface has no way to count or iterate over all
-  // aliases, so we have to fall back to SQL for this function.
-  /** @var \Drupal\Core\Path\AliasStorageInterface $alias_storage */
-  $alias_storage = \Drupal::service('path.alias_storage');
-  $connection = \Drupal::database();
-  $schema = $connection->schema();
-  if ($schema->tableExists('url_alias')) {
-    if (!isset($sandbox['current'])) {
-      $sandbox['current'] = 0;
-      $sandbox['max'] = $connection->query('SELECT COUNT(pid) FROM {url_alias}')
-        ->fetchField();
-    }
-    $aliases = $connection->queryRange('SELECT pid, source, alias, langcode FROM {url_alias} ORDER BY pid ASC', $sandbox['current'], $sandbox['current'] + 50)
-      ->fetchAllAssoc('pid', PDO::FETCH_ASSOC);
-
-    foreach ($aliases as $alias) {
-      $alias_storage->save($alias['source'], $alias['alias'], $alias['langcode'], $alias['pid']);
-      $sandbox['current']++;
-    }
-
-    $sandbox['#finished'] = empty($sandbox['max']) ? 1 : ($sandbox['current'] / $sandbox['max']);
-    return t('Path aliases converted');
-  }
-  else {
-    return t('Path alias conversion skipped, because the {url_alias} table did not exist.');
-  }
-}
-
-/**
  * @} End of "addtogroup updates-8.0.0-beta".
  */