Entity API in combination with Routing API is one of the most robust and developed in Drupal. What is particular about it is that it heavily relies on configuration. Entity annotations and routing YAML files have everything an entity needs to function, but no code. For some developers, it is a black box; for others, it is a sleek language, removing all repetitive functionality and reducing 100 lines of boilerplate code to 3 fully descriptive ones.
The power of configuration in Drupal — not so widely used, but where it truly shines — is that: