Roblox Interview Questions — Page 9

Roblox·Software Engineer·Technical Phone Screen

Jun 2026

Roblox SWE interview with a coding problem centered on building part of a real-time analytics backend. The problem was straightforward on the surface but the efficiency angle is where things get interesting.

You're building a component for a real-time analytics system. Given a sequence of update and query operations on named experiences, implement a function that tracks each experience's total earnings and returns the top earner on every query.

“My first instinct was just a hashmap for totals and a linear scan on every query, which works but feels bad when you imagine thousands of queries hitting a large dataset.”

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Roblox·Software Engineer·Hiring Manager Screen

Jun 2026

Behavioral round at Roblox for a senior software engineering role, focused almost entirely on influence and ownership. One meaty question about driving a project through internal resistance, with a bunch of follow-ups probing whether you actually owned the persuasion or just had a manager run interference for you.

Walk me through a significant project you drove. What was your role, what was the hardest part, and specifically: who pushed back when you started it, why did they object, and how did you actually get them on board?
If you hadn't been able to win the skeptic over, what would you have done? Would you have dropped it, escalated, or pushed forward anyway?
Looking back, was the person who opposed your project at least partially right? Did their objection end up improving the design?
How do you distinguish between pushback you should actually incorporate versus resistance you should push through?
Tell me about a time your persuasion failed and you couldn't get a key stakeholder on board. What happened?

“This is the whole interview basically.”

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

Jun 2026

Roblox ML Engineer interview centered on a full system design for a recommendation engine. The scope was pretty wide and they clearly wanted to see how you'd hold the whole thing together end to end, not just rattle off buzzwords.

Design a complete recommendation system from scratch for a product of your choice, covering candidate generation, ranking, re-ranking, and serving architecture.
How would you handle latency requirements at the p99 level for a recommendation system serving millions of users?
How do you approach cold start for both new users and new items in a recommendation system?
Walk me through how you'd evaluate a recommendation model both offline and online, and how you'd reconcile when they disagree.
What are the trade-offs between model freshness and serving cost in a production recommendation system?

“This was basically the whole interview.”

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Roblox·Data Scientist·Technical Phone Screen

Jun 2026

Roblox data scientist round with a pandas question around cleaning up friendship data from raw request logs. Pretty focused, one problem, not a lot of fluff.

Given a table of friend request logs, write Python/pandas code that returns each unique friendship pair exactly once (with the smaller user ID listed first) along with the date the friendship was accepted.

“The core idea is simple enough: filter to accepted requests, normalize the id ordering so (1,2) and (2,1) don't show up as separate rows, then deduplicate.”

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Roblox·Machine Learning Engineer·Technical Phone Screen

Jun 2026

Roblox ML engineer screen that turned into a pretty deep systems exercise. Started simple but they kept adding constraints until I was basically designing a streaming frequency tracker from scratch.

Given a list of log entries where each entry contains a function or call name (and possibly a timestamp and other fields), find the most frequently occurring function call. Be prepared to extend this to top-k results, time-windowed queries, streaming inputs, tie-breaking, and call-stack or caller-callee pair analysis.

“I started with the obvious hashmap approach and felt pretty good about it.”

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Roblox·Software Engineer·Technical Phone Screen

Jun 2026

Roblox software engineer interview with a coding round focused on rate limiting. The problem had a clean core but the follow-up extensions kept coming, which I wasn't fully ready for.

Implement a rate limiter that allows up to N requests within a sliding window of T seconds. The API should have an allow(timestamp) method that returns whether the request is permitted and updates internal state.
How would you handle memory cleanup for idle keys in the per-key rate limiter variant?
What are the thread-safety concerns with this rate limiter, and how would you avoid a single global lock when supporting many concurrent clients?

“Got the deque approach pretty fast.”

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Roblox·Software Engineer·Onsite - System Design / Architecture

Jun 2026

System design round at Roblox for a software engineering role, one big open-ended question about building a scheduled payments platform. The scope was massive and I don't think I covered everything they wanted, but it was a genuinely interesting problem to work through.

Design a scheduled payment system where users can set a future-dated payment and cancel it before it runs. Cover the APIs, data model, job scheduling, idempotency, time zone handling, failure/retry logic, consistency with the payment gateway, security and PCI compliance, scaling strategy, monitoring, disaster recovery, and capacity estimates.

“This was basically the whole interview in one question.”

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Roblox·Software Engineer·Technical Phone Screen

Jun 2026

Roblox coding round for a software engineer role, three-part problem built around game-event aggregation. The structure was incremental: get the base working first, then layer on follow-ups rather than starting over each time.

Design and implement a class that ingests game-event records (player ID, event type, timestamp, payload) and supports querying aggregates like per-player event counts or totals, both globally and per player.
Extend the query API to support a sliding time window, returning only aggregates for events that occurred within the last K minutes.
Further extend the system to handle bulk event ingestion, out-of-order event delivery, and per-player breakdowns efficiently.

“The base case felt manageable.”

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Roblox·Software Engineer·Technical Phone Screen

Jun 2026

Roblox SWE interview that built on a previous call-stack parsing problem, adding two progressively harder variants back to back. Pretty focused session, no fluff.

Given a trace of enter/exit events representing function calls, find the longest call stack depth observed at any point during execution.
Extend the same enter/exit event trace to a multi-threaded scenario where each event includes a thread ID. Return the maximum call stack for each thread independently.

“This is the follow-up to the basic call-stack parser, so you're expected to already have the core structure in your head.”

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Roblox·Product Manager·Onsite - Product Sense / Strategy

Jun 2026

Got a product design question at Roblox that sounds cute until you actually try to answer it. Designing for 5-year-olds is deceptively hard and I don't think I nailed it.

Design a coding game intended for 5-year-old children.

“I went straight to mechanics and completely forgot to anchor on the user first.”

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