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Roblox·Data Scientist·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Roblox data scientist interview had a pandas/Python question built around an e-commerce orders dataset. Pretty standard analytics stuff but the multi-part structure meant you had to keep your head straight and not rush through it.

Questions Asked (1)

Q1

Given an orders dataset in pandas, do three things: find the highest-priced order per user, compute the overall average order price, and break down total orders and average price by calendar day.

Product Analytics & MetricsAlgorithms & Data Structures
Author's notes

The idxmax part tripped me up a little.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the dataset schema and assumptions (e.g., price column, user ID, date column). Then walk through each task using pandas operations: groupby with idxmax for highest-priced order per user, mean for overall average, and groupby with agg for daily breakdown. Emphasize efficient, vectorized solutions and discuss trade-offs.

Pro tip: Mention that you'd validate the date column's type and handle missing values before grouping, and that you'd use named aggregations for clarity and performance.

1. Clarify schema and assumptions

Ask about column names, data types, and any missing values. Confirm that 'price' is numeric and 'date' is datetime.

2. Highest-priced order per user

Use groupby('user_id')['price'].idxmax() to get indices, then loc to retrieve full rows. Alternatively, sort_values and drop_duplicates.

3. Overall average order price

Compute df['price'].mean() directly, ensuring no NaNs or handling them appropriately.

4. Daily breakdown of orders and average price

Group by date (e.g., df.groupby(df['date'].dt.date).agg(total_orders=('order_id','count'), avg_price=('price','mean'))).

5. Review and optimize

Check for edge cases (e.g., ties in max price) and discuss performance considerations for large datasets.

Key Points to Mention

  • Use of groupby with idxmax for per-user max price
  • Handling ties when multiple orders have the same highest price
  • Named aggregations for clarity and efficiency
  • Ensuring date column is datetime and extracting date component
  • Vectorized operations over loops for performance
  • Validation of results (e.g., sum of daily orders equals total orders)

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.