•SYSTEM DESIGN
Roblox System Design Questions
6 distinct system design problems asked at Roblox from September 2025 to September 2026, merged from 8 candidate reports. Each one links to a full solution.
Sources: PracHub, LeetCode discussions. Sorted by how often the problem was reported at Roblox.
Design Multi-Dimensional Request Rate Limiting
Design a distributed rate limiter that protects APIs by limiting requests (or consumed units such as LLM billing tokens or storage quota) per user, API key, tenant, or IP. It must support configurable rules (e.g., 100…
Also reported as: Design a rate limiter
Design a Scalable Likes System
Design a scalable likes system for posts or games: users like and unlike items, see whether they have liked something, and see like counts. Popular items receive huge bursts of likes (hot keys). Requirements: each user can like…
Also reported as: Design a Scalable Like Counter
Design a Real-Time Shared To-Do List
Design a to-do list service: users create, read, update, delete, complete and reorder tasks in lists. The basic version focuses on REST API design, authentication, rate limiting, caching and API versioning. The real-time variant…
Design a Played-By Summary System
Design a 'played by your friends' social-proof feature for a game platform: on each game page, show a user how many of their friends (and which ones) played that game recently. Discuss maintaining the friend graph, recording play…
Design a Reusable Dropdown Menu Component
Design a reusable, production-grade dropdown (select) menu UI component for a design system. Discuss its public API (props), controlled vs uncontrolled state, keyboard navigation and accessibility (ARIA roles, focus management),…
Design favorites and social game recommendations
Design a recommendation system from scratch, for example recommending posts, games, local sports teams or weekly deals to users. Cover candidate generation (collaborative filtering, content-based, social signals, location),…
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