I've been using Varnish with my Drupal sites for quite a long while (as a replacement to the Drupal anonymous page cache). I've just started using Drupal 8 and naturally want to use Varnish for those sites as well. If you've been using Varnish with Drupal in the past, you've already wrapped your head around the complexities of front-end anonymous page caching, presumably, and you know that the varnish module was responsible for translating/passing the Drupal page cache-clear requests to Varnish - explicitly from the performance page, but also as a side effect of editing nodes, etc. But if you've been paying attention to Drupal 8, you'll know that it's much smarter about cache clearing. Rather than relying on explicit calls to clear specific or all cached pages, it uses ' cache tags ' which require another layer of abstraction in your brain to understand. Specifically, the previous mechanism in Drupal 7 and earlier was by design 'conservative...