The Symfony Service Container in Drupal 8 gives us new capability to alter core’s behaviour without needing to apply hacks.  Just swapping out a core service for our own implementation, or even assuming that a service still uses the core implementation, might not always be safe though.
This session will walk through how the service container allows us to easily change components within Drupal core without patches, and how to do it safely so that things are less likely to break during site upgrades or when other modules also need to alter the same component.

View the presentation slides