Quick start for integrators 

Change specific cache options 

By default, most Core caches use the database backend. The default cache configuration is defined in EXT:core/Configuration/DefaultConfiguration.php (GitHub) and can be overridden in config/system/settings.php.

If specific settings should be applied to the configuration, they should be added to config/system/settings.php. All settings in config/system/settings.php will be merged with DefaultConfiguration.php. The easiest way to see the final cache configuration is to use the TYPO3 backend module System > Configuration > $GLOBALS['TYPO3_CONF_VARS'] (with installed lowlevel system extension).

Example for a configuration of a Redis cache backend on Redis database number 42 instead of the default database backend with compression for the pages cache:

<?php

use TYPO3\CMS\Core\Cache\Backend\RedisBackend;

return [
    // ...
    'SYS' => [
        // ...
        'caching' => [
            // ...
            'cacheConfigurations' => [
                // ...
                'pages' => [
                    'backend' => RedisBackend::class,
                    'options' => [
                        'database' => 42,
                    ],
                ],
            ],
        ],
    ],
];

Garbage collection task 

Most cache backends do not have an internal system to remove old cache entries that exceeded their lifetime. A cleanup must be triggered externally to find and remove those entries, otherwise caches could grow to arbitrary size. This could lead to a slow website performance, might sum up to significant hard disk or memory usage and could render the server system unusable.

It is advised to always enable the scheduler and run the "Caching framework garbage collection" task to retain clean and small caches. This housekeeping could be done once a day when the system is otherwise mostly idle.