This module provides a combination L1/L2 cache using a combination of APCu as L1 with a database as L2 (and for coherency management among the L1 caches).

Currently only supported on Pantheon, but there's nothing that inherently relies on anything Pantheon-specific.

Upstream library: https://github.com/lcache/lcache

1. Upload the module to your site. a. If using Composer to manage your site's modules:

   composer require drupal/lcache
   

   b. If not using Composer:

   drush dl lcache
   cd sites/all/modules/lcache
   composer install --no-dev
   

   c. If you are pushing to a remote location (e.g. Pantheon) you will need to force-commit the 'vendor' directory so that the core lcache library is pushed along with the module:

   git add --force vendor
   git push origin master
   

2. Install the module (so Drupal creates the database schema).

3. Configure settings.php to use the cache:

   $conf['cache_backends'][] = 'sites/all/modules/lcache/lcache.cache.inc';
   $conf['cache_default_class'] = 'LCache';
   // The 'cache_form' bin must be assigned to non-volatile storage.
   // And if you use page cache, you probably don't want it in LCache.
   $conf['cache_class_cache_form'] = 'DrupalDatabaseCache';
   $conf['cache_class_cache_page'] = 'DrupalDatabaseCache';
   

Composer Manager is not officially supported for use with LCache, but there are reports of it working properly by adding the following early (before LCache is included) in settings.php:

require_once DRUPAL_ROOT . '/sites/all/modules/composer_manager/composer_manager.module';
composer_manager_register_autoloader();