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System Design questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master system design interviews.

What difficulty level is this interview question?

This is a medium difficulty System Design question, commonly asked during Onsite rounds at Roblox.

What role is this question designed for?

This question is commonly asked for Software Engineer candidates at Roblox during technical interviews.

Design favorites and social game recommendations

Q: Design favorites and social game recommendations

This question evaluates a candidate's ability to design scalable backend systems for social features, assessing competencies in data modeling, event-driven ingestion, caching strategies, privacy handling, idempotent operations, and recommendation ranking.

Problem

Design a backend system for a gaming app that supports:

Favorites ("Fav") : users can favorite/unfavorite games and view their favorites list.
Social recommendations : show recommended games such as "Your friends played this game" / "Popular among your friends" .

Assume the product has tens of millions of users and a large game catalog.

Requirements

Functional

Favorite/unfavorite a game.
List a user’s favorited games (paginated, sorted by most recent).
Generate a social recommendation feed for a user based on friends’ activity:
- Friends who played a game recently
- Friends who favorited/liked a game
- Optional: trending in your friend network

Non-functional

Low latency for reads (favorites list and recommendations).
Correctness guarantees for favorites (no duplicates; idempotent operations).
Handle privacy settings (e.g., user hides activity; blocked users).
Scalable ingestion of play/favorite events.
Reasonable freshness (e.g., within minutes) for recommendations.

Output

Describe APIs, data/storage design, event pipeline, recommendation logic/ranking, caching, and how you would scale and measure quality.

Problem

Design a backend system for a gaming app that supports:

Favorites ("Fav") : users can favorite/unfavorite games and view their favorites list.

Social recommendations : show recommended games such as "Your friends played this game" / "Popular among your friends" .

Assume the product has tens of millions of users and a large game catalog.

Requirements

Functional

Favorite/unfavorite a game.

List a user’s favorited games (paginated, sorted by most recent).

Generate a social recommendation feed for a user based on friends’ activity:

Friends who played a game recently
Friends who favorited/liked a game
Optional: trending in your friend network

Non-functional

Low latency for reads (favorites list and recommendations).

Correctness guarantees for favorites (no duplicates; idempotent operations).

Handle privacy settings (e.g., user hides activity; blocked users).

Scalable ingestion of play/favorite events.

Reasonable freshness (e.g., within minutes) for recommendations.

Output

Describe APIs, data/storage design, event pipeline, recommendation logic/ranking, caching, and how you would scale and measure quality.

Design favorites and social game recommendations

Quick Overview

Problem

Requirements

Functional

Non-functional

Output

Solution

Comments (0)

Design favorites and social game recommendations

Quick Overview

Problem

Requirements

Functional

Non-functional

Output

Solution

Comments (0)