RuboCop introduces the new server options for super fast mode.
RuboCop 2.0 has the catchphrase RuboCop 2x2, like Ruby 3x3. the server mode is a big move towards that. This is perfect for the current era where quick feedback to developer is required, especially when interacting with text editors and IDEs.
Through the design and implementation of server options, you will get the essence of how fast RuboCop works.