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┌───────────────┐ ┌───────────────┐ ┌───────────────┐
│ User UI │──────▶│ Review Service│──────▶│ Database │
└───────────────┘ └───────────────┘ └───────────────┘
│ │ ▲
│ │ │
│ │ │
└──────────────────────┴──────────────────────┘
Aggregated Ratings Cache
This diagram shows users submitting reviews through the UI, which the Review Service processes and stores in the database. An aggregated ratings cache speeds up average rating retrieval.
### Before: No enforcement of single review per user per item class Review: def __init__(self, user_id, item_id, rating, comment): self.user_id = user_id self.item_id = item_id self.rating = rating self.comment = comment reviews = [] def add_review(review): reviews.append(review) ### After: Enforce one review per user per item with update support class Review: def __init__(self, user_id, item_id, rating, comment): self.user_id = user_id self.item_id = item_id self.rating = rating self.comment = comment reviews = {} # Key: (user_id, item_id) def add_or_update_review(review): key = (review.user_id, review.item_id) reviews[key] = review # Example usage r1 = Review('user1', 'item1', 5, 'Great product!') add_or_update_review(r1) r2 = Review('user1', 'item1', 4, 'Changed my mind, still good.') add_or_update_review(r2) print(reviews[("user1", "item1")].rating) # Outputs: 4
current_avg = 4.0
num_reviews = 5
new_rating = 5
new_avg = (current_avg * num_reviews + new_rating) / (num_reviews + 1)
new_avg?