The database cache backend supports specifying a serializer

To allow the the serialization to be swapped for more performant implementations, the database cache backend no longer hardcodes using PHP's serialize() / unserialize() for serialization, but allows passing in a serializer. By default PHP's serializer is passed in. The igbinary module provides alternate serializers which may improve performance.

// DatabaseBackendFactory::get() before this change
return new DatabaseBackend($this->connection, $this->checksumProvider, $bin, $max_rows);

// DatabaseBackendFactory::get() after this change.
return new DatabaseBackend($this->connection, $this->checksumProvider, $bin, $this->serializer, $max_rows);

These constructors were also affected by https://www.drupal.org/node/3387233

# Database cache backend in core.services.yml
cache.backend.database:
  class: Drupal\Core\Cache\DatabaseBackendFactory
  arguments: ['@database', '@cache_tags.invalidator.checksum', '@settings', '@serialization.phpserialize']

# Example database cache backend with igbinary module
cache.backend.database:
  class: Drupal\Core\Cache\DatabaseBackendFactory
  arguments: ['@database', '@cache_tags.invalidator.checksum', '@settings', '@serialization.igbinary']

Other change notices for same issue

• The serializer service is passed as new parameter to DatabaseBackendFactory and DatabaseBackend constructors
• ObjectAwareSerializationInterface is introduced for serializers that can serialize and deserialize PHP objects