agaric-coop/box/docs/extras/memcached.md

Memcached is an in-memory caching system, much like Redis. While Varnish is generally used to improve performance for anonymous users, memcached is used to improve the performance for logged in users.

To enable Memcached in Drupal VM:

1. Make sure memcached is in the list of installed_extras in your config.yml.
2. Install the Memcache API module.
3. Enable the module before you configure it in the next step.
4. Add the following to your settings.php

// Make memcache the default cache class.
$settings['cache']['default'] = 'cache.backend.memcache';

There's a lot more configuration available and the best resource is generally the Memcache API module's README.

For a list of available role variables, see the geerlingguy.memcached Ansible role's README.