Rating and review system in LLD - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main purpose of a rating and review system?

To collect user feedback in the form of ratings and written reviews to help others make informed decisions.

beginner

Name two common data elements stored in a review entry.

User ID (who wrote the review) and rating value (usually a number like 1 to 5).

intermediate

Why is it important to handle duplicate reviews in a rating system?

To prevent users from submitting multiple reviews for the same item, which can skew the overall rating and reduce trust.

advanced

How can a rating and review system scale to handle millions of users?

By using caching for popular items, sharding databases, and asynchronous processing for review submissions.

intermediate

What is a common approach to calculate the average rating efficiently?

Store and update the total sum of ratings and count of reviews to compute the average without scanning all reviews each time.

Which data structure is best to quickly retrieve all reviews for a product?

A Stack of reviews

B Linked list of all reviews

C Hash map with product ID as key and list of reviews as value

D Queue of reviews

A hash map allows fast lookup by product ID to get all related reviews.

What is a common rating scale used in review systems?

A 1 to 5 stars

B 1 to 100 points

C True or False

D Red, Yellow, Green

1 to 5 stars is a widely accepted and easy-to-understand rating scale.

Why should reviews be moderated or filtered?

A To increase the number of reviews

B To remove spam and inappropriate content

C To make the system slower

D To hide negative feedback

Moderation ensures quality and trustworthiness by filtering spam or harmful content.

Which technique helps reduce database load when showing average ratings?

A Precomputing and storing average ratings

B Recalculating average on every request

C Deleting old reviews

D Using a single database for all data

Precomputing averages avoids expensive calculations on every request.

What is a key challenge in designing a rating and review system?

A Allowing unlimited reviews per user per item

B Making reviews invisible

C Ignoring user feedback

D Handling fake or biased reviews

Detecting and preventing fake or biased reviews is crucial for system reliability.

Explain how you would design a scalable rating and review system for an e-commerce platform.

Think about how to store data, keep it accurate, and serve many users quickly.

Describe the flow of a user submitting a review and how the system processes it.

Consider each step from user action to data update.