Roblox Interview Questions
Practice the exact questions companies are asking right now.
Design a rate limiter
Problem: Design a Rate Limiter Design a rate limiting service to protect an API from abuse and to provide fair usage. Requirements - The API gateway (...
How to estimate feature impact on usage time
Problem A product team believes a new feature (or a variable you can influence, e.g., enabling notifications, new feed ranking, new UI) changes user t...
Find maximum follow depth using recursion
You are given a directed follows relationship representing a social graph: - Each record (follower_id, followee_id) means follower_id follows followee...
Design a game recommendation modeling approach
Scenario You are building a personalized game recommender for a consumer app/store. The goal is to recommend a ranked list of games to each user to in...
Write SQL for influence score and follower growth
You are working on a social product with these tables: Tables / Schemas users - user_id BIGINT (PK) - created_at TIMESTAMP posts - post_id BIGINT (PK)...
Extend counter to per-client rate limiting
You are extending the recent-requests counter to support per-client rate limiting. Each request now includes a clientId identifying the caller. You mu...
Implement four DS coding tasks
You are completing a CodeSignal-style assessment (Python or R). Implement solutions for the following four independent questions. 1) Two-sample z-test...
Rank queries by prefix, frequency, and time
You are given three arrays of the same length n: - queries[i]: a non-empty string representing the text of the i-th query. - timestamps[i]: an integer...
Find most frequent call stack from logs
Given an array of log entries for a single-threaded program's function calls, each entry is either '->Name' (function entry) or '<-Name' (function exi...
Design a scheduled payment system
System Design: Scheduled Payment Service Context You are designing a backend service that allows end users to: - Schedule a payment for a future date/...
Implement queue-based rate limiter with multi-key limits
Implement a rate limiter with method allow(timestamp) that returns true if a request is allowed under a limit of K requests per rolling window W milli...
Optimize bread-factory pipeline for max profit
You can assemble a production line by choosing modules of three types: Mixers, Ovens, Packers. Each module i has (type, build_cost_i, throughput_i uni...
Implement recent-requests counter
You are designing an in-memory component for a web service that needs to track how many requests ("hits") it has received in the last 5 minutes. Imple...
Design real-time game matchmaking service
Design a Real-Time Game Matchmaking Service Context You are designing the matchmaking subsystem for an online multiplayer game that supports multiple ...
Design sliding-window rate limiter with multi-keys
Design a Precise Sliding-Window Rate Limiter Context You are designing a rate limiter for an API that must enforce a true sliding-window limit (i.e., ...
Simulate robot path and detect boundedness
A robot starts at (0, 0) facing north on an infinite 2D plane. It executes a command string s consisting of 'G' (move forward one unit), 'L' (turn lef...
Design ad revenue A/B with guardrails
Mobile App Ads Marketplace: Experiment Plan to Lift Revenue by 10% in 60 Days Context You run a mobile app ads marketplace. Target is to increase ad r...
Implement robust one/two-sided p-value function
Implement p_value(stat, alternative, dist, df=None) Context: You're building a small, production-quality helper to compute p-values for common one- an...
Describe resolving revenue–UX metric conflict
Behavioral: Leading a High-Stakes Revenue vs. UX Trade-off Context: You led a decision where ads revenue goals conflicted with user-experience metrics...
Design resource loader and ROS-like pub/sub
System Design: Resource Loader and ROS-like Publish/Subscribe Context You are designing two foundational systems for a large-scale, real-time interact...