diff --git a/src/wp-includes/user.php b/src/wp-includes/user.php
index 0b522b022235e..c81c6aae7d96c 100644
--- a/src/wp-includes/user.php
+++ b/src/wp-includes/user.php
@@ -682,14 +682,25 @@ function count_many_users_posts( $users, $post_type = 'post', $public_only = fal
 		return $pre;
 	}
 
-	$userlist = implode( ',', array_map( 'absint', $users ) );
-	$where    = get_posts_by_author_sql( $post_type, true, null, $public_only );
+	// Cleanup the users array. Remove duplicates and sort for consistent ordering.
+	$users = array_unique( array_filter( array_map( 'absint', (array) $users ) ) );
+	sort( $users );
 
-	$result = $wpdb->get_results( "SELECT post_author, COUNT(*) FROM $wpdb->posts $where AND post_author IN ($userlist) GROUP BY post_author", ARRAY_N );
+	$userlist    = implode( ',', $users );
+	$cache_key   = 'count_many_users_posts:' . md5( implode( ':', array( $post_type, $public_only ? 'public' : 'public|private', $userlist, get_current_user_id() ) ) );
+	$cache_salts = array( wp_cache_get_last_changed( 'posts' ), wp_cache_get_last_changed( 'users' ) );
+	$count       = wp_cache_get_salted( $cache_key, 'user-queries', $cache_salts );
 
-	$count = array_fill_keys( $users, 0 );
-	foreach ( $result as $row ) {
-		$count[ $row[0] ] = $row[1];
+	if ( false === $count ) {
+		$where  = get_posts_by_author_sql( $post_type, true, null, $public_only );
+		$result = $wpdb->get_results( "SELECT post_author, COUNT(*) FROM $wpdb->posts $where AND post_author IN ($userlist) GROUP BY post_author", ARRAY_N );
+
+		$count = array_fill_keys( $users, 0 );
+		foreach ( $result as $row ) {
+			$count[ $row[0] ] = $row[1];
+		}
+
+		wp_cache_set_salted( $cache_key, $count, 'user-queries', $cache_salts, HOUR_IN_SECONDS );
 	}
 
 	return $count;
diff --git a/tests/phpunit/tests/user.php b/tests/phpunit/tests/user.php
index 535004ee560a8..ea25853796a3f 100644
--- a/tests/phpunit/tests/user.php
+++ b/tests/phpunit/tests/user.php
@@ -604,6 +604,48 @@ public function test_count_many_users_posts() {
 		$this->assertSame( '1', $counts[ $user_id_b ] );
 	}
 
+	/**
+	 * Test salted cache functionality for count_many_users_posts().
+	 *
+	 * @ticket 63405
+	 */
+	public function test_count_many_users_posts_salted_cache() {
+		// Clear any existing cache
+		wp_cache_flush();
+
+		$author_id = self::factory()->user->create( array( 'role' => 'author' ) );
+		$editor_id = self::factory()->user->create( array( 'role' => 'editor' ) );
+
+		// Create posts for both users
+		self::factory()->post->create( array( 'post_author' => $author_id ) );
+		self::factory()->post->create( array( 'post_author' => $editor_id ) );
+
+		// Test cache hit
+		$counts1 = count_many_users_posts( array( $author_id, $editor_id ), 'post', false );
+		$counts2 = count_many_users_posts( array( $author_id, $editor_id ), 'post', false );
+		$this->assertSame( $counts1, $counts2 );
+		$this->assertSame( '1', $counts1[ $author_id ] );
+		$this->assertSame( '1', $counts1[ $editor_id ] );
+
+		// Test cache invalidation - create new post for author only
+		self::factory()->post->create( array( 'post_author' => $author_id ) );
+		$counts3 = count_many_users_posts( array( $author_id, $editor_id ), 'post', false );
+		$this->assertSame( '2', $counts3[ $author_id ] );
+		$this->assertSame( '1', $counts3[ $editor_id ] );
+
+		// Test different post types use different cache keys
+		self::factory()->post->create(
+			array(
+				'post_author' => $author_id,
+				'post_type'   => 'page',
+			)
+		);
+		$counts_posts = count_many_users_posts( array( $author_id ), 'post', false );
+		$counts_pages = count_many_users_posts( array( $author_id ), 'page', false );
+		$this->assertSame( '2', $counts_posts[ $author_id ] );
+		$this->assertSame( '1', $counts_pages[ $author_id ] );
+	}
+
 	/**
 	 * @ticket 22858
 	 */