diff -u b/core/modules/media/src/Entity/Media.php b/core/modules/media/src/Entity/Media.php
--- b/core/modules/media/src/Entity/Media.php
+++ b/core/modules/media/src/Entity/Media.php
@@ -10,7 +10,6 @@
 use Drupal\media\MediaInterface;
 use Drupal\media\MediaSourceEntityConstraintsInterface;
 use Drupal\media\MediaSourceFieldConstraintsInterface;
-use Drupal\media\PrepareSaveInterface;
 use Drupal\user\UserInterface;
 
 /**
@@ -84,7 +83,7 @@
  *   }
  * )
  */
-class Media extends EditorialContentEntityBase implements MediaInterface, PrepareSaveInterface {
+class Media extends EditorialContentEntityBase implements MediaInterface {
 
   use StringTranslationTrait;
 
@@ -375,15 +374,22 @@
   }
 
   /**
-   * {@inheritdoc}
+   * Sets the media entity's field values from the source's metadata.
+   *
+   * Fetching the metadata could be slow (e.g., if requesting it from a remote
+   * API), so this is called by \Drupal\media\MediaStorage::save() prior to it
+   * beginning the database transaction, whereas static::preSave() executes
+   * after the transaction has already started.
+   *
+   * @internal
+   *   Expose this as an API in
+   *   https://www.drupal.org/project/drupal/issues/2992426.
    */
   public function prepareSave() {
     // @todo If the source plugin talks to a remote API (e.g. oEmbed), this code
     // might be performing a fair number of HTTP requests. This is dangerously
     // brittle and should probably be handled by a queue, to avoid doing HTTP
-    // operations during entity save. As it is, doing this before calling
-    // parent::save() is a quick-fix to avoid doing HTTP requests in the middle
-    // of a database transaction (which begins once we call parent::save()). See
+    // operations during entity save. See
     // https://www.drupal.org/project/drupal/issues/2976875 for more.
 
     // In order for metadata to be mapped correctly, $this->original must be
diff -u b/core/modules/media/src/MediaStorage.php b/core/modules/media/src/MediaStorage.php
--- b/core/modules/media/src/MediaStorage.php
+++ b/core/modules/media/src/MediaStorage.php
@@ -19,13 +19,14 @@
    */
   public function save(EntityInterface $media) {
     // For backwards compatibility, modules that override the Media entity
-    // class, are not required to implement \Drupal\media\PrepareSaveInterface.
-    if ($media instanceof PrepareSaveInterface) {
+    // class, are not required to implement the prepareSave() method.
+    // @todo For Drupal 8.7, consider throwing a deprecation notice if the
+    //   method doesn't exist. See
+    //   https://www.drupal.org/project/drupal/issues/2992426 for further
+    //   discussion.
+    if (method_exists($media, 'prepareSave')) {
       $media->prepareSave();
     }
-    else {
-      // @todo For Drupal 8.7, consider throwing a deprecation notice.
-    }
     return parent::save($media);
   }
 
reverted:
--- b/core/modules/media/src/PrepareSaveInterface.php
+++ /dev/null
@@ -1,27 +0,0 @@
-<?php
-
-namespace Drupal\media;
-
-
-/**
- * Interface definition for executing code before a save transaction begins.
- *
- * Media sources could leverage external API's to fetch metadata. The external
- * calls could be slow and when they run inside a database transaction, could
- * lock the database causing issues for other users.
- *
- * @internal
- *
- * @todo Consider making this a non-internal interface in Drupal 8.7.
- */
-interface PrepareSaveInterface {
-
-  /**
-   * Prepares the media entity to be saved.
-   *
-   * This is executed by the storage handler's save() method prior to beginning
-   * the database transaction.
-   */
-  public function prepareSave();
-
-}