Roblox Interview Questions — Page 1

Roblox·Software Engineer·Onsite - Multi Round

Apr 2025

Went through the full Roblox SWE Game Developer pipeline starting in April, covering an OA, recruiter screen, portfolio review, technical round, and eventually a behavioral after getting re-opened by the hiring manager. Got rejected twice despite both the portfolio and behavioral rounds seeming to go well, and the technical being derailed mid-way by a cheating accusation that felt completely unfair.

Walk us through your game development portfolio and the projects you've shipped.
Solve a technical coding problem, then extend your solution to handle a follow-up variant.
Behavioral round covering your experiences and how you've handled various situations in past work.

“This part went fine, maybe the best part of the whole process.”

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Roblox·Data Scientist·Technical Phone Screen

Sep 2025

This was a deep technical screen for a DS role at Roblox, basically one giant experiment design question that covered everything from randomization to power calculations to ecosystem interference. The question was exhaustive and felt more like a take-home prompt than a live interview, which threw me off a bit.

Roblox is replacing an existing homepage tab with a new one. Design a rigorous experiment to evaluate the causal impact of this change at both the user and ecosystem levels.
What experimental unit and randomization scheme would you use, and how would you prevent cross-device contamination?
What primary success metrics and guardrail metrics would you define for this experiment?
How would you measure and mitigate novelty effects and navigation friction caused by removing a tab?
How would you handle network effects and ecosystem interference between creators and users across experiment arms?
How would you define your metrics at a user-day grain, and would you use CUPED or pre-exposure covariates for variance reduction?
Walk through a sample size and power calculation for detecting a 1% relative lift in D7 retention at 80% power and alpha 0.05, including how weekly seasonality affects minimum test duration.
What decision thresholds and rollback criteria would you set for this experiment?
If click-through on the new tab increases but D7 retention falls, what diagnostics would you run?
If treatment cannibalizes time from other tabs but improves long-term retention, what follow-up analysis design would you use?

“This question is basically nine questions stitched together.”

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Roblox·Machine Learning Engineer·Onsite - System Design / Architecture

Apr 2026

Interviewed for an ML engineer role at Roblox and got a system design question about detecting bot players. Pretty open-ended, which I wasn't fully prepared for.

How would you design a system to detect bot players in a gaming platform?

“I went straight to feature engineering, things like click patterns, movement speed, session length, and tried to sketch out a pipeline from data collection to model serving.”

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Roblox·Software Engineer·Onsite - System Design / Architecture

Apr 2026

System design round at Roblox for a software engineering role, centered entirely on building a matchmaking system. Pretty deep dive, they wanted real architecture not just buzzwords.

Design a matchmaking system that groups multiple players into game sessions, covering skill-based matching, latency, queue time, party support, and regional pools.

“This one sprawled fast.”

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Roblox·Machine Learning Engineer·Technical Phone Screen

Apr 2026

Had a technical screen for an ML Engineer role at Roblox where they asked me to walk through one of my published papers. The research presentation angle was a bit unexpected and I felt underprepared for how deep the follow-ups went on transferability to their actual product.

Walk us through one of your published papers or research projects, covering the problem you tackled, your approach, and the key results. Then explain how the techniques could apply to our product or business context.

“I picked a paper I knew cold but totally fumbled the pivot to Roblox's use cases.”

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Roblox·Software Engineer·Onsite - System Design / Architecture

Apr 2026

Roblox system design round focused entirely on building a rate-limiter service. Pretty deep dive, they wanted real trade-offs not just a surface-level answer.

Design a rate-limiter service, including the API interface, choice of algorithm, single-node vs distributed architecture, handling of clock skew and bursty traffic, multi-tier limits, fail-open vs fail-closed behavior, and how to communicate limits back to clients.

“This is one of those questions where you think you know it and then you open your mouth and realize how many corners there are.”

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Roblox·Machine Learning Engineer·Onsite - System Design / Architecture

Apr 2026

ML system design round at Roblox for an MLE role. Built out a game recommendation system and landed somewhere in the middle: no real disasters, but didn't finish the pipeline either. Still not sure how you're supposed to cover everything in an hour once the interviewer starts drilling.

Design a recommendation system for surfacing games to users on the platform.

“Spent way too long on features and modeling.”

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Roblox·Software Engineer·Onsite - System Design / Architecture

Apr 2026

System design round at Roblox for a software engineer role, centered entirely on designing a URL shortener from scratch. Pretty classic question but the scope they expected was surprisingly wide, covering everything from key generation to analytics pipelines.

Design a URL-shortening service similar to TinyURL or bit.ly, supporting short alias generation, redirects, optional custom aliases, expiration, and basic click analytics.
What database would you choose for storing URL mappings and how would you partition it at billions-of-records scale?
How would you design the caching layer to handle hot or frequently accessed URLs, and what eviction strategy makes sense here?
How would you implement rate limiting to prevent abuse of the alias generation endpoint?
Walk through how you'd build the analytics pipeline to track click counts without impacting redirect latency.

“I started with the read/write ratio and worked outward from there, which felt right.”

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Roblox·Software Engineer·Technical Phone Screen

Apr 2026

Roblox technical phone screen, graph problem, nothing too exotic but the follow-up caught me a little flat-footed.

Given a number of courses and a list of prerequisite pairs, determine whether it's possible to complete all courses without hitting a circular dependency.

“I went with Kahn's algorithm, tracking indegrees and peeling off nodes with zero dependencies via BFS.”

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Roblox·Machine Learning Engineer·Technical Phone Screen

Apr 2026

Roblox ML engineer interview, technical phone screen focused entirely on a rate limiting design problem with a per-client twist. Pretty systems-heavy for an ML role, which I wasn't expecting.

Design and implement a per-client rate limiter class that tracks hits separately for each client ID over a rolling 5-minute window, supporting hit(clientId, timestamp) and getHits(clientId, timestamp) operations with amortized O(1) time and space proportional to recent hits.

“My first instinct was to reach for a hashmap of queues, one queue per client storing timestamps, and just pop off anything older than 300 seconds on each call.”

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