diff --git a/core/lib/Drupal/Core/Batch/BatchStorage.php b/core/lib/Drupal/Core/Batch/BatchStorage.php
index 82f5b65767..c25ec7af1f 100644
--- a/core/lib/Drupal/Core/Batch/BatchStorage.php
+++ b/core/lib/Drupal/Core/Batch/BatchStorage.php
@@ -200,6 +200,8 @@ protected function catchException(\Exception $e) {
 
   /**
    * Defines the schema for the batch table.
+   *
+   * @internal
    */
   public function schemaDefinition() {
     return [
diff --git a/core/lib/Drupal/Core/Cache/DatabaseBackend.php b/core/lib/Drupal/Core/Cache/DatabaseBackend.php
index 82f0054093..747186b9b7 100644
--- a/core/lib/Drupal/Core/Cache/DatabaseBackend.php
+++ b/core/lib/Drupal/Core/Cache/DatabaseBackend.php
@@ -461,6 +461,8 @@ protected function normalizeCid($cid) {
 
   /**
    * Defines the schema for the {cache_*} bin tables.
+   *
+   * @internal
    */
   public function schemaDefinition() {
     $schema = [
diff --git a/core/lib/Drupal/Core/Cache/DatabaseCacheTagsChecksum.php b/core/lib/Drupal/Core/Cache/DatabaseCacheTagsChecksum.php
index 450b4411a1..0c4faee341 100644
--- a/core/lib/Drupal/Core/Cache/DatabaseCacheTagsChecksum.php
+++ b/core/lib/Drupal/Core/Cache/DatabaseCacheTagsChecksum.php
@@ -163,6 +163,8 @@ protected function ensureTableExists() {
 
   /**
    * Defines the schema for the {cachetags} table.
+   *
+   * @internal
    */
   public function schemaDefinition() {
     $schema = [
diff --git a/core/lib/Drupal/Core/Config/DatabaseStorage.php b/core/lib/Drupal/Core/Config/DatabaseStorage.php
index 5d88f1576e..8a749a38c7 100644
--- a/core/lib/Drupal/Core/Config/DatabaseStorage.php
+++ b/core/lib/Drupal/Core/Config/DatabaseStorage.php
@@ -180,6 +180,8 @@ protected function ensureTableExists()  {
 
   /**
    * Defines the schema for the configuration table.
+   *
+   * @internal
    */
   protected static function schemaDefinition() {
     $schema = [
diff --git a/core/lib/Drupal/Core/Flood/DatabaseBackend.php b/core/lib/Drupal/Core/Flood/DatabaseBackend.php
index 12e9102af0..cb1fc92503 100644
--- a/core/lib/Drupal/Core/Flood/DatabaseBackend.php
+++ b/core/lib/Drupal/Core/Flood/DatabaseBackend.php
@@ -185,6 +185,8 @@ protected function catchException(\Exception $e) {
 
   /**
    * Defines the schema for the flood table.
+   *
+   * @internal
    */
   public function schemaDefinition() {
     return [
diff --git a/core/lib/Drupal/Core/Lock/DatabaseLockBackend.php b/core/lib/Drupal/Core/Lock/DatabaseLockBackend.php
index 0984ffcb1f..8afcefe21f 100644
--- a/core/lib/Drupal/Core/Lock/DatabaseLockBackend.php
+++ b/core/lib/Drupal/Core/Lock/DatabaseLockBackend.php
@@ -239,6 +239,8 @@ protected function normalizeName($name) {
 
   /**
    * Defines the schema for the semaphore table.
+   *
+   * @internal
    */
   public function schemaDefinition() {
     return [
diff --git a/core/lib/Drupal/Core/Menu/MenuTreeStorage.php b/core/lib/Drupal/Core/Menu/MenuTreeStorage.php
index c50f7b431a..f6578fe63e 100644
--- a/core/lib/Drupal/Core/Menu/MenuTreeStorage.php
+++ b/core/lib/Drupal/Core/Menu/MenuTreeStorage.php
@@ -1217,6 +1217,8 @@ protected function definitionFields() {
    *
    * @return array
    *   The schema API definition for the SQL storage table.
+   *
+   * @internal
    */
   protected static function schemaDefinition() {
     $schema = [
diff --git a/core/lib/Drupal/Core/Path/AliasStorage.php b/core/lib/Drupal/Core/Path/AliasStorage.php
index 4f380125bb..a02bc3534d 100644
--- a/core/lib/Drupal/Core/Path/AliasStorage.php
+++ b/core/lib/Drupal/Core/Path/AliasStorage.php
@@ -406,6 +406,8 @@ protected function catchException(\Exception $e) {
 
   /**
    * Defines the schema for the {url_alias} table.
+   *
+   * @internal
    */
   public static function schemaDefinition() {
     return [
diff --git a/core/lib/Drupal/Core/Queue/DatabaseQueue.php b/core/lib/Drupal/Core/Queue/DatabaseQueue.php
index e70000ee22..d0d1fb9415 100644
--- a/core/lib/Drupal/Core/Queue/DatabaseQueue.php
+++ b/core/lib/Drupal/Core/Queue/DatabaseQueue.php
@@ -277,6 +277,8 @@ protected function catchException(\Exception $e) {
 
   /**
    * Defines the schema for the queue table.
+   *
+   * @internal
    */
   public function schemaDefinition() {
     return [
diff --git a/core/lib/Drupal/Core/Routing/MatcherDumper.php b/core/lib/Drupal/Core/Routing/MatcherDumper.php
index 5e329f7daf..0de728892f 100644
--- a/core/lib/Drupal/Core/Routing/MatcherDumper.php
+++ b/core/lib/Drupal/Core/Routing/MatcherDumper.php
@@ -194,6 +194,8 @@ protected function ensureTableExists() {
    *
    * @return array
    *   The schema API definition for the SQL storage table.
+   *
+   * @internal
    */
   protected function schemaDefinition() {
     $schema = [
diff --git a/core/modules/views/src/Tests/ViewKernelTestBase.php b/core/modules/views/src/Tests/ViewKernelTestBase.php
index b39bc7473a..5a23285918 100644
--- a/core/modules/views/src/Tests/ViewKernelTestBase.php
+++ b/core/modules/views/src/Tests/ViewKernelTestBase.php
@@ -126,6 +126,8 @@ protected function executeView($view, array $args = []) {
 
   /**
    * Returns the schema definition.
+   *
+   * @internal
    */
   protected function schemaDefinition() {
     return ViewTestData::schemaDefinition();
diff --git a/core/modules/views/src/Tests/ViewTestBase.php b/core/modules/views/src/Tests/ViewTestBase.php
index 8d09a0940d..1d9dccf584 100644
--- a/core/modules/views/src/Tests/ViewTestBase.php
+++ b/core/modules/views/src/Tests/ViewTestBase.php
@@ -131,6 +131,8 @@ protected function executeView(ViewExecutable $view, $args = []) {
 
   /**
    * Returns the schema definition.
+   *
+   * @internal
    */
   protected function schemaDefinition() {
     return ViewTestData::schemaDefinition();
diff --git a/core/modules/views/src/Tests/ViewTestData.php b/core/modules/views/src/Tests/ViewTestData.php
index 3c9ace7555..27ddf7c465 100644
--- a/core/modules/views/src/Tests/ViewTestData.php
+++ b/core/modules/views/src/Tests/ViewTestData.php
@@ -58,6 +58,8 @@ public static function createTestViews($class, array $modules) {
 
   /**
    * Returns the schema definition.
+   *
+   * @internal
    */
   public static function schemaDefinition() {
     $schema['views_test_data'] = [
diff --git a/core/modules/views/tests/src/Functional/ViewTestBase.php b/core/modules/views/tests/src/Functional/ViewTestBase.php
index 0465f966c3..10bc5d48bc 100644
--- a/core/modules/views/tests/src/Functional/ViewTestBase.php
+++ b/core/modules/views/tests/src/Functional/ViewTestBase.php
@@ -136,6 +136,8 @@ protected function executeView(ViewExecutable $view, $args = []) {
 
   /**
    * Returns the schema definition.
+   *
+   * @internal
    */
   protected function schemaDefinition() {
     return ViewTestData::schemaDefinition();
diff --git a/core/modules/views/tests/src/Kernel/Handler/FilterCombineTest.php b/core/modules/views/tests/src/Kernel/Handler/FilterCombineTest.php
index e5d37119df..feffbafd9e 100644
--- a/core/modules/views/tests/src/Kernel/Handler/FilterCombineTest.php
+++ b/core/modules/views/tests/src/Kernel/Handler/FilterCombineTest.php
@@ -290,6 +290,8 @@ protected function dataSet() {
 
   /**
    * Allow {views_test_data}.job to be NULL.
+   *
+   * @internal
    */
   protected function schemaDefinition() {
     $schema = parent::schemaDefinition();
diff --git a/core/modules/views/tests/src/Kernel/Handler/FilterStringTest.php b/core/modules/views/tests/src/Kernel/Handler/FilterStringTest.php
index c24cc6ff03..03c1b878a5 100644
--- a/core/modules/views/tests/src/Kernel/Handler/FilterStringTest.php
+++ b/core/modules/views/tests/src/Kernel/Handler/FilterStringTest.php
@@ -39,6 +39,9 @@ public function viewsData() {
     return $data;
   }
 
+  /**
+   * {@inheritdoc}
+   */
   protected function schemaDefinition() {
     $schema = parent::schemaDefinition();
     $schema['views_test_data']['fields']['description'] = [
diff --git a/core/modules/views/tests/src/Kernel/Plugin/RelationshipJoinTestBase.php b/core/modules/views/tests/src/Kernel/Plugin/RelationshipJoinTestBase.php
index 1163297b1b..19d5e9554b 100644
--- a/core/modules/views/tests/src/Kernel/Plugin/RelationshipJoinTestBase.php
+++ b/core/modules/views/tests/src/Kernel/Plugin/RelationshipJoinTestBase.php
@@ -44,6 +44,8 @@ protected function setUpFixtures() {
    * Overrides \Drupal\views\Tests\ViewTestBase::schemaDefinition().
    *
    * Adds a uid column to test the relationships.
+   *
+   * @internal
    */
   protected function schemaDefinition() {
     $schema = parent::schemaDefinition();
diff --git a/core/modules/views/tests/src/Kernel/ViewsKernelTestBase.php b/core/modules/views/tests/src/Kernel/ViewsKernelTestBase.php
index f149b7fba1..4bbe402863 100644
--- a/core/modules/views/tests/src/Kernel/ViewsKernelTestBase.php
+++ b/core/modules/views/tests/src/Kernel/ViewsKernelTestBase.php
@@ -129,6 +129,8 @@ protected function executeView($view, array $args = []) {
 
   /**
    * Returns the schema definition.
+   *
+   * @internal
    */
   protected function schemaDefinition() {
     return ViewTestData::schemaDefinition();
diff --git a/core/modules/views_ui/tests/src/Functional/HandlerTest.php b/core/modules/views_ui/tests/src/Functional/HandlerTest.php
index 826cdc24e5..31829941fc 100644
--- a/core/modules/views_ui/tests/src/Functional/HandlerTest.php
+++ b/core/modules/views_ui/tests/src/Functional/HandlerTest.php
@@ -42,6 +42,8 @@ protected function setUp($import_test_views = TRUE) {
    * Overrides \Drupal\views\Tests\ViewTestBase::schemaDefinition().
    *
    * Adds a uid column to test the relationships.
+   *
+   * @internal
    */
   protected function schemaDefinition() {
     $schema = parent::schemaDefinition();