Roblox Interview Questions — Page 14

Roblox·Data Scientist·Technical Phone Screen

Jul 2026

Got a technical screen for a Data Scientist role at Roblox that was pretty much one big coding/stats problem. The whole thing centered on implementing a difference-in-differences estimator with a pre-trend check, which I wasn't expecting to write from scratch in an interview setting.

You're given panel data as three arrays (period, group, outcome). Implement a difference-in-differences estimator using the latest pre-period and earliest post-period, then validate parallel pre-trends by checking whether the max gap in treatment-control differences across all pre-periods falls within a given threshold.

“This wrecked me a little at first.”

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Roblox·Machine Learning Engineer·Technical Phone Screen

Jul 2026

Roblox ML engineer interview that went deep on recommendation systems. One long design question covering basically the entire ML lifecycle, from raw features to live A/B tests. Not a casual screen.

Design a game recommendation system for users. Cover the full ML pipeline: feature engineering, candidate generation, model selection, training data construction, loss functions, optimizers, offline metrics, and online experimentation.

“This is a lot to cover in one question and I definitely didn't pace myself well.”

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Roblox·Software Engineer·Online Assessment (OA)

Jul 2026

Took the Roblox OA and now I'm sitting here second-guessing everything. The CodeSignal was surprisingly easy but the simulation problems, especially the Mars drone one, did some damage. Roblox really loves 2D arrays right now.

Factory simulation problem: navigate and manage a factory environment programmatically.
Mars drone simulation: write functions to control a drone navigating across maps, then apply those functions under test conditions.
Matrix traversal or manipulation problem (two separate questions), with the second requiring optimization from a naive to a more efficient solution.

“Spent a decent chunk of time on this one and I'm still not sure how I did.”

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Roblox·Software Engineer·Technical Phone Screen

Jul 2026

Roblox technical phone screen for a software engineer role. The problem was a digit-sum bucketing question with some spicy follow-ups that I wasn't fully prepared for.

Given two integers low and high (inclusive), define s(x) as the sum of the digits of x. Group every integer in [low, high] by its digit sum, and return the size of the largest group. What's your algorithm and its time and space complexity?
When the range high minus low is extremely large, can you avoid iterating over every integer in the range?
How would your approach change if the numbers were represented in an arbitrary base b (where b can range from 2 to 36)?

“The core problem isn't bad.”

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Roblox·Software Engineer·Technical Phone Screen

Jul 2026

Roblox coding round with one meaty grid simulation problem. Two phases to implement, which sounds manageable until you're actually in it trying to keep track of what counts as a run and then simulating gravity correctly.

Given an m x n grid of single digits, first find all horizontal or vertical consecutive runs of the same digit with length 3 or more, returning each as [row, col, length] sorted top-to-bottom then left-to-right. Then remove all cells belonging to those runs, let the remaining digits fall down within their columns, and fill the top with zeros. Return the final grid.

“The two-phase structure is what gets you.”

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Roblox·Data Scientist·Technical Phone Screen

Jul 2026

Roblox data scientist interview with a pretty gnarly SQL question that tests your ability to handle deduplication logic, window functions, and multi-step aggregation all at once. One question, but it's a lot of question.

Write a SQL query to compute, for each campaign over a 7-day window, total impressions, total charged clicks (deduplicating multiple clicks on the same ad request to only count the earliest), CTR, RPM, and standard deviation of daily RPM. Filter to campaigns with at least 10,000 impressions and order by RPM descending then stddev ascending.

“The dedup rule is what makes this hard.”

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Roblox·Data Scientist·Technical Phone Screen

Jul 2026

SQL-heavy technical screen for a DS role at Roblox. Two questions, both around a social graph schema with users, posts, engagement events, and follows. Nothing behavioral, just pure query writing the whole time.

Given a social product schema with users, posts, engagement events, and follows tables, write a SQL query that computes each user's influence score, defined as the total number of engagement events their posts received plus their total follower count.
Using the same schema, write a SQL query that computes monthly follower growth per user, including new followers gained each month, the previous month's new follower count via LAG, a month-over-month growth rate with divide-by-zero handling, and a cumulative running total of followers.

“My first instinct was to do both aggregations in one big join and i immediately tangled myself up with duplicate counts.”

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Roblox·Software Engineer·Onsite - System Design / Architecture

Jul 2026

Roblox system design round focused entirely on rate limiting, which sounds straightforward until they start layering on multi-dimensional constraints and distributed deployment concerns. Pretty deep dive for a single question.

Design a sliding-window rate limiter that enforces a global cap of R requests within any rolling T-second window. Cover the public interface, data structures, time resolution, and time/space complexity.
Extend the rate limiter so each request carries a userId and userExperience field, and both dimensions are rate-limited independently and concurrently. How do you structure keys and counters without double-counting across dimensions?
How would you evict stale state from the rate limiter efficiently as the window slides forward?
How do you deploy and scale this rate limiter in a distributed environment? Address sharding, coordination between nodes, clock skew, and idempotency.
How would you test this rate limiter for correctness, including burst traffic, boundary timestamps, and window rollover edge cases?

“I started with a circular buffer approach and talked through how a true sliding window differs from fixed-window bucketing.”

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Roblox·Data Scientist·Technical Phone Screen

Jul 2026

Roblox data scientist interview that went deep into auction theory, specifically GSP vs VCG mechanics with quality scores. The questions were more rigorous than I expected for a DS role, felt closer to a research economist interview at points.

Given a two-slot auction with position CTRs, three advertisers with bids and quality scores, and a reserve price, walk through the GSP allocation and per-click pricing. Then compute expected revenue and total welfare.
Using the same auction setup, compute each winner's per-click price under VCG with quality scores and a reserve price. How does platform revenue compare to GSP?
Under GSP, assuming the other advertisers bid truthfully, is there a profitable bid shading strategy for advertiser B? Find a shading range that keeps B in the same slot but lowers their price.
How does budget pacing (a multiplicative bid dampening factor between 0 and 1) interact with quality-adjusted ranking in an auction? Between GSP and VCG, which mechanism holds up better for truthful reporting when advertisers are budget-constrained?

“This took me longer than it should have.”

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Roblox·Data Scientist·Onsite - System Design / Architecture

Jul 2026

Roblox data scientist interview with a deep ML system design question. One question, very technical, the kind where you can tell they actually want to see if you've built this stuff before and not just read about it.

Design a full end-to-end ML pipeline to predict whether a machine will experience a fault within the next 24 hours, evaluated at each hour. Your design needs to cover leakage prevention with a feature store strategy, time-based cross-validation with explicit cutoffs, handling ~1% class imbalance with cost-sensitive thresholding (FN=$10,000, FP=$500), probability calibration and feature importance with SHAP caveats, and robustness to sensor missingness, outliers, and distribution drift.

“This was a lot.”

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