Amazon calculates a product’s star ratings based on a machine learned model instead of a raw data average. The model takes into account factors including the age of a rating, whether the ratings are from verified purchasers, and factors that establish reviewer trustworthiness.
The best part about the book was the types of microservice patterns described which was covered in good detail. I felt that an example could be used that would provided a strong visual of how microservices are designed and run. Such examples were missing in the book.