varnish-8.x-1.x-dev/varnish.services.yml

services:
  cache.backend.varnish:
    class: Drupal\varnish\Cache\VarnishBackendFactory
  cache.varnish:
    class: Drupal\Core\Cache\CacheBackendInterface
    tags:
      - { name: cache.bin, default_backend: cache.backend.varnish }
    factory: cache_factory:get
    arguments: [varnish]