tmp-platform-swr/web/index.php

<?php
// First visit -> 5s, times match
// Second visit -> instant, times don't match
// … T+14 -> instant, times don't match
// … T+15 (or 16) -> instant, times match (or almost)
// Nothing for 30s -> 5s, times match
header('Cache-Control: s-max-age=60, stale-while-revalidate=20');
sleep(5);
print('This is a slow test with data cached for 10s but updated smartly. ' . 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>
  <li><a href="./compromise.php">A good compromise to deal with slow pages fast</a></li>
</ul>
<p id="js-date"></p>
<script type="text/javascript">
  document.getElementById('js-date').innerText = new Date().toISOString();
</script>