Other tries

web/index.php

@@ -1,8 +1,12 @@
 <?php
-header('Cache-Control: max-age=20, stale-while-revalidate=80');
-sleep(10);
+header('Cache-Control: s-max-age=10, stale-while-revalidate=20');
+sleep(5);
 print('This is a slow test. ' . date('Y-m-d H:i:s'));
 ?>
+<ul>
+  <li><a href="./slow.php">Slow</a></li>
+  <li><a href="./slow-but-fast.php">Slow but fast</a></li>
+</ul>
 <p id="js-date"></p>
 <script type="text/javascript">
   document.getElementById('js-date').innerText = new Date().toISOString();

web/slow-but-fast.php

@@ -0,0 +1,9 @@
+<?php
+header('Cache-Control: s-max-age=1, stale-while-revalidate=20');
+sleep(5);
+print('This is a slow instant test. ' . date('Y-m-d H:i:s'));
+?>
+<p id="js-date"></p>
+<script type="text/javascript">
+  document.getElementById('js-date').innerText = new Date().toISOString();
+</script>

web/slow.php

@@ -0,0 +1,9 @@
+<?php
+header('Cache-Control: s-max-age=10');
+sleep(5);
+print('This is a slow instant test. ' . date('Y-m-d H:i:s'));
+?>
+<p id="js-date"></p>
+<script type="text/javascript">
+  document.getElementById('js-date').innerText = new Date().toISOString();
+</script>