LLD - Design — Food Delivery System
A rating system stores average rating and count per product. After deleting a review, the average becomes incorrect. What is the likely cause?
A rating system stores average rating and count per product. After deleting a review, the average becomes incorrect. What is the likely cause?
medium📝 Analysis Q14 of 15
Step-by-Step Solution
Solution:
Step 1: Understand average calculation
Average = sum of ratings / count of reviews. Both must be accurate.Step 2: Identify deletion impact
If count is not decreased after deleting a review, average calculation divides by wrong count.Final Answer:
Not updating the count of reviews after deletion -> Option CQuick Check:
Count mismatch causes wrong average [OK]
Quick Trick: Always update count when reviews change [OK]
Common Mistakes:
- Ignoring count update after deletion
- Assuming recalculation always fixes average
- Confusing data structure choice with calculation error
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