What constitutes a good "reference architecture"?

A question to cloud architects, developers, and administrators ...

Have you used "reference architectures" in your work to migrate or develop cloud workloads? If yes, do you have any examples of what you would consider to be good reference architectures? Even if you can't share any examples, if you have any ideas around what content you think a good reference architecture should include, please share your thoughts. Your input will be used to improve the quality and usefulness of Google Cloud reference architectures. Thank you!