Wayfair·Data Scientist·Online Assessment (OA)
Jun 2026
Wayfair data scientist OA with two tasks back to back, SQL and Python. The SQL one had a tricky time-window filter that I almost misread, and the Python function had more edge cases than I expected for something that looked straightforward on the surface.
- Given a customers table and a purchases table, write a SQL query to find the customer(s) with the highest purchase price within the earliest 10-year window of purchase history. Return all tied customers if applicable.
- Write a Python function using pandas that cleans a student scores DataFrame by dropping students missing two or more scores, imputing remaining nulls with per-column medians, then returning the top 5 students sorted by math score descending, physics score descending, and student ID ascending.
“The 10-year window thing tripped me up.” The rest of the author's notes on Data Scientist interview at Wayfair, Online Assessment (OA) round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.
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