diff --git a/core/includes/update.inc b/core/includes/update.inc
index 5aff2bc..4aca085 100644
--- a/core/includes/update.inc
+++ b/core/includes/update.inc
@@ -345,9 +345,9 @@ function update_module_add_to_system($modules = array()) {
 function update_fix_d8_requirements() {
   global $conf;
 
-  if (drupal_get_installed_schema_version('system') < 8000 && !variable_get('update_d8_requirements', FALSE)) {
+  if (drupal_get_installed_schema_version('system') < 8000 && !update_variable_get('update_d8_requirements', FALSE)) {
     // @todo: Make critical, first-run changes to the database here.
-    variable_set('update_d8_requirements', TRUE);
+    update_variable_set('update_d8_requirements', TRUE);
   }
 }
 
@@ -958,6 +958,75 @@ function update_retrieve_dependencies() {
 }
 
 /**
+ * Gets the value of a variable directly from the database during the 7.x-8.x upgrade path.
+ *
+ * Use this during the 7.x-8.x upgrade path instead of variable_get().
+ *
+ * @param string $name
+ *   The name of the variable.
+ * @param mixed $default
+ *   The default value of the variable.
+ *
+ * @return mixed
+ *   The value of the variable in the database unserialized, or NULL if not set.
+ *
+ * @see update_variable_set()
+ * @see update_variable_del()
+ * @ingroup config_upgrade
+ */
+function update_variable_get($name, $default = NULL) {
+  $result = db_query('SELECT value FROM {variable} WHERE name = :name', array(':name' => $name))->fetchField();
+  if ($result !== FALSE) {
+    return unserialize($result);
+  }
+  return $default;
+}
+
+/**
+ * Sets a persistent variable during the 7.x-8.x upgrade path.
+ *
+ * Use this during the 7.x-8.x upgrade path instead of variable_set().
+ *
+ * @param string $name
+ *   The name of the variable to set.
+ * @param mixed $value
+ *   The value to set. This can be any PHP data type; these functions take care
+ *   of serialization as necessary.
+ *
+ * @see update_variable_get()
+ * @see update_variable_del()
+ * @ingroup config_upgrade
+ */
+function update_variable_set($name, $value) {
+  db_merge('variable')
+    ->key(array(
+      'name' => $name,
+    ))
+    ->fields(array(
+      'value' => serialize($value),
+    ))
+    ->execute();
+}
+
+/**
+ * Delete a variable from the database during the 7.x-8.x upgrade path.
+ *
+ * Use this during the 7.x-8.x upgrade path instead of variable_del().
+ *
+ * @param string $name
+ *   The name of the variable to delete.
+ *
+ * @see update_variable_get()
+ * @see update_variable_set()
+ * @ingroup config_upgrade
+ */
+function update_variable_del($name) {
+  db_delete('variable')
+    ->condition('name', $name)
+    ->execute();
+}
+
+/**
  * Updates config with values set on Drupal 7.x
  *
  * Provide a generalised method to migrate variables from Drupal 7 to Drupal 8's
diff --git a/core/modules/block/block.install b/core/modules/block/block.install
index 8fcecbe..4c5149b 100644
--- a/core/modules/block/block.install
+++ b/core/modules/block/block.install
@@ -245,7 +245,7 @@ function block_update_dependencies() {
  * @ingroup config_upgrade
  */
 function block_update_8000() {
-  variable_del('block_cache');
+  update_variable_del('block_cache');
 }
 
 /**
diff --git a/core/modules/locale/locale.install b/core/modules/locale/locale.install
index 35106ae..334b401 100644
--- a/core/modules/locale/locale.install
+++ b/core/modules/locale/locale.install
@@ -195,27 +195,27 @@ function locale_update_8000() {
 function locale_update_8001() {
   // Only change language_types if we had this setting saved. Keep order
   // of types because that is significant for value dependency.
-  $types = variable_get('language_types', NULL);
+  $types = update_variable_get('language_types', NULL);
   if (!empty($types) && isset($types['language'])) {
     $new_types = array();
     foreach ($types as $key => $type) {
       $new_types[$key == 'language' ? 'language_interface' : $key] = $type;
     }
-    variable_set('language_types', $new_types);
+    update_variable_set('language_types', $new_types);
   }
 
   // Rename language_negotiation_language setting if exists.
-  $setting = variable_get('language_negotiation_language', NULL);
+  $setting = update_variable_get('language_negotiation_language', NULL);
   if ($setting !== NULL) {
-    variable_set('language_negotiation_language_interface', $setting);
-    variable_del('language_negotiation_language');
+    update_variable_set('language_negotiation_language_interface', $setting);
+    update_variable_del('language_negotiation_language');
   }
 
   // Rename locale_language_providers_weight_language setting if exists.
-  $weight = variable_get('locale_language_providers_weight_language', NULL);
+  $weight = update_variable_get('locale_language_providers_weight_language', NULL);
   if ($weight !== NULL) {
-    variable_set('locale_language_providers_weight_language_interface', $weight);
-    variable_del('locale_language_providers_weight_language');
+    update_variable_set('locale_language_providers_weight_language_interface', $weight);
+    update_variable_del('locale_language_providers_weight_language');
   }
 
   // Update block data in all core block related tables. Contributed modules
@@ -281,7 +281,7 @@ function locale_update_8002() {
  */
 function locale_update_8003() {
   $message = '';
-  $domains = variable_get('locale_language_negotiation_url_domains', array());
+  $domains = update_variable_get('locale_language_negotiation_url_domains', array());
   // $used_domains keeps track of the domain names in use.
   $used_domains = array();
   foreach ($domains as $langcode => $domain) {
@@ -301,7 +301,7 @@ function locale_update_8003() {
       }
     }
   }
-  variable_set('locale_language_negotiation_url_domains', $domains);
+  update_variable_set('locale_language_negotiation_url_domains', $domains);
 
   if (!empty($message)) {
     return $message;
@@ -314,11 +314,11 @@ function locale_update_8003() {
  * @ingroup config_upgrade
  */
 function locale_update_8004() {
-  $types = variable_get('language_types', NULL);
+  $types = update_variable_get('language_types', NULL);
   if (!empty($types)) {
     foreach ($types as $type => $configurable) {
       // Rename the negotiation and language switch callback keys.
-      $negotiation = variable_get('language_negotiation_' . $type, NULL);
+      $negotiation = update_variable_get('language_negotiation_' . $type, NULL);
       if (!empty($negotiation)) {
         foreach ($negotiation as $method_id => &$method) {
           $method['callbacks']['negotiation'] = $method['callbacks']['language'];
@@ -328,14 +328,14 @@ function locale_update_8004() {
             unset($method['callbacks']['switcher']);
           }
         }
-        variable_set('language_negotiation_' . $type, $negotiation);
+        update_variable_set('language_negotiation_' . $type, $negotiation);
       }
 
       // Rename the language negotiation methods weight variable.
-      $weight = variable_get('locale_language_providers_weight_' . $type , NULL);
+      $weight = update_variable_get('locale_language_providers_weight_' . $type , NULL);
       if ($weight !== NULL) {
-        variable_set('language_negotiation_methods_weight_' . $type , $weight);
-        variable_del('locale_language_providers_weight_' . $type);
+        update_variable_set('language_negotiation_methods_weight_' . $type , $weight);
+        update_variable_del('locale_language_providers_weight_' . $type);
       }
     }
   }
@@ -486,7 +486,7 @@ function locale_update_8007() {
   );
   // Add all language type weight variables. As the function language_types()
   // is not available its functionality is rebuild.
-  $language_types = variable_get('language_types', array(
+  $language_types = update_variable_get('language_types', array(
     LANGUAGE_TYPE_INTERFACE => TRUE,
     LANGUAGE_TYPE_CONTENT => FALSE,
     LANGUAGE_TYPE_URL => FALSE,
@@ -515,7 +515,7 @@ function locale_update_8007() {
     'locale-session' => 'language-session',
   );
   foreach ($variable_names as $variable_name) {
-    $value = variable_get($variable_name);
+    $value = update_variable_get($variable_name);
     // Skip processing if the variable is not stored in the db.
     if ($value === NULL) {
       continue;
@@ -544,7 +544,7 @@ function locale_update_8007() {
     if (stristr($variable_name, 'language_negotiation_methods_weight_') !== FALSE) {
       asort($new_value);
     }
-    variable_set($variable_name, $new_value);
+    update_variable_set($variable_name, $new_value);
   }
 }
 
@@ -562,10 +562,10 @@ function locale_update_8008() {
   );
   foreach ($variable_name_map as $deprecated_variable_name => $new_variable_name) {
     // Check if this variable is stored in the db and if so rename it.
-    $value = variable_get($deprecated_variable_name);
+    $value = update_variable_get($deprecated_variable_name);
     if ($value !== NULL) {
-      variable_set($new_variable_name, $value);
-      variable_del($deprecated_variable_name);
+      update_variable_set($new_variable_name, $value);
+      update_variable_del($deprecated_variable_name);
     }
   }
 }
diff --git a/core/modules/node/node.install b/core/modules/node/node.install
index 7382320..cdf39b9 100644
--- a/core/modules/node/node.install
+++ b/core/modules/node/node.install
@@ -522,11 +522,11 @@ function _update_7000_node_get_types() {
 function node_update_8001() {
   $types = db_query('SELECT type FROM {node_type}')->fetchCol();
   foreach ($types as $type) {
-    $node_type_language = variable_get('language_content_type_' . $type);
+    $node_type_language = update_variable_get('language_content_type_' . $type);
     if (isset($node_type_language)) {
-      variable_set('node_type_language_' . $type, $node_type_language);
+      update_variable_set('node_type_language_' . $type, $node_type_language);
     }
-    variable_del('language_content_type_' . $type);
+    update_variable_del('language_content_type_' . $type);
   }
 }
 
@@ -550,20 +550,20 @@ function node_update_8002() {
 function node_update_8003() {
   $types = db_query('SELECT type FROM {node_type}')->fetchCol();
   foreach ($types as $type) {
-    variable_set('node_type_language_default_' . $type, LANGUAGE_NOT_SPECIFIED);
-    $node_type_language = variable_get('node_type_language_' . $type, 0);
+    update_variable_set('node_type_language_default_' . $type, LANGUAGE_NOT_SPECIFIED);
+    $node_type_language = update_variable_get('node_type_language_' . $type, 0);
     if ($node_type_language == 0) {
-      variable_set('node_type_language_hidden_' . $type, TRUE);
+      update_variable_set('node_type_language_hidden_' . $type, TRUE);
     }
     if ($node_type_language == 2) {
       // Translation was enabled, so enable it again and
       // unhide the language selector. Because if language is
       // LANGUAGE_NOT_SPECIFIED and the selector hidden, translation
       // cannot be enabled.
-      variable_set('node_type_language_hidden_' . $type, FALSE);
-      variable_set('node_type_language_translation_enabled_' . $type, TRUE);
+      update_variable_set('node_type_language_hidden_' . $type, FALSE);
+      update_variable_set('node_type_language_translation_enabled_' . $type, TRUE);
     }
-    variable_del('node_type_language_' . $type);
+    update_variable_del('node_type_language_' . $type);
   }
 }
 
diff --git a/core/modules/system/lib/Drupal/system/Tests/Upgrade/LanguageUpgradePathTest.php b/core/modules/system/lib/Drupal/system/Tests/Upgrade/LanguageUpgradePathTest.php
index 489fe90..f9f76a7 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Upgrade/LanguageUpgradePathTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Upgrade/LanguageUpgradePathTest.php
@@ -110,7 +110,7 @@ class LanguageUpgradePathTest extends UpgradePathTestBase {
     );
     // Check that locale_language_providers_weight_language is correctly
     // renamed.
-    $current_weights = variable_get('language_negotiation_methods_weight_language_interface', array());
+    $current_weights = update_variable_get('language_negotiation_methods_weight_language_interface', array());
     $this->assertTrue(serialize($expected_weights) == serialize($current_weights), t('Language negotiation method weights upgraded.'));
 
     // Look up migrated plural string.
@@ -137,7 +137,7 @@ class LanguageUpgradePathTest extends UpgradePathTestBase {
   public function testLanguageUrlUpgrade() {
     $language_domain = 'ca.example.com';
     db_update('languages')->fields(array('domain' => 'http://' . $language_domain . ':8888'))->condition('language', 'ca')->execute();
-    variable_set('locale_language_negotiation_url_part', 1);
+    $this->variable_set('locale_language_negotiation_url_part', 1);
 
     $this->assertTrue($this->performUpgrade(), t('The upgrade was completed successfully.'));
 
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index 96c02c3..cb66777 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -1720,8 +1720,8 @@ function system_update_8000() {
 function system_update_8001() {
   $themes = array('theme_default', 'maintenance_theme', 'admin_theme');
   foreach ($themes as $theme) {
-    if (variable_get($theme) == 'garland') {
-      variable_set($theme, 'bartik');
+    if (update_variable_get($theme) == 'garland') {
+      update_variable_set($theme, 'bartik');
     }
   }
 }
@@ -1748,13 +1748,13 @@ function system_update_8001() {
  * @ingroup config_upgrade
  */
 function system_update_8002() {
-  $front_page = variable_get('site_frontpage');
+  $front_page = update_variable_get('site_frontpage');
   if (!isset($front_page)) {
-    variable_set('site_frontpage', 'node');
+    update_variable_set('site_frontpage', 'node');
   }
-  $theme = variable_get('theme_default');
+  $theme = update_variable_get('theme_default');
   if (!isset($theme)) {
-    variable_set('theme_default', 'bartik');
+    update_variable_set('theme_default', 'bartik');
   }
 }
 
@@ -1886,7 +1886,7 @@ function system_update_8007() {
  * Remove the 'clean_url' configuration variable.
  */
 function system_update_8008() {
-  variable_del('clean_url');
+  update_variable_del('clean_url');
 }
 
 /**