BlogController.php

<?php

use Symfony\Component\HttpFoundation\Response;
// ...

public function index()
{
    // somehow create a Response object, like by rendering a template
    $response = $this->render('blog/index.html.twig', []);

    // cache for 3600 seconds
    $response->setSharedMaxAge(3600);
  
    /*
    $response->setCache([
        'etag'          => $etag,
        'last_modified' => $date,
        'max_age'       => 10,
        's_maxage'      => 10,
        'public'        => true,
        // 'private'    => true,
    ]);
    */

    // (optional) set a custom Cache-Control directive
    $response->headers->addCacheControlDirective('must-revalidate', true);

    return $response;
}

CacheKernel.php

<?php

namespace App;

use Symfony\Bundle\FrameworkBundle\HttpCache\HttpCache;

class CacheKernel extends HttpCache
{
  protected function getOptions()
    {
        return [
            'default_ttl' => 0,
            // more infos on https://github.com/symfony/symfony/blob/4.3/src/Symfony/Component/HttpKernel/HttpCache/HttpCache.php
        ];
    }
}

index.php

<?php

+ use App\CacheKernel;
use App\Kernel;

// ...
$kernel = new Kernel($_SERVER['APP_ENV'], (bool) $_SERVER['APP_DEBUG']);

+ // Wrap the default Kernel with the CacheKernel one in 'prod' environment
+ if ('prod' === $kernel->getEnvironment()) {
+     $kernel = new CacheKernel($kernel);
+ }

$request = Request::createFromGlobals();