Went through the Walmart Global Tech data scientist interview loop in Q1 2026. Four rounds. Writing this up because the DS interview at Walmart is legitimately different from a typical DS loop at a pure-tech company.
Round structure: Recruiter screen (30 min, mostly background + team fit) SQL + data wrangling round (60 min with a senior DS) Case study / business problem round (60 min with DS lead + stakeholder PM) Stats and ML round (60 min with senior DS and a scientist)
SQL round. Harder than I expected. Not HackerRank easy-medium. They gave me a schema that was genuinely Walmart-ish: fact table for transactions, dimension tables for stores, products, suppliers. Questions included: Find stores with declining YoY sales in Q4 but positive QoQ in Q3 (date manipulation heavy) Identify the top-10 products by revenue that were out of stock for more than 3 days in the last 90 days (join + window function) Write a query to detect duplicate supplier records based on fuzzy name matching (this one I'd never seen in an interview, used LIKE + GROUP BY and talked through the limitations)
They cared about whether I talked through my reasoning, not just whether I got a working query. When I wrote something suboptimal, the interviewer flagged it and said "this would be slow on billions of rows, how would you rewrite it?"
Case round. Very applied. I got: "Walmart is seeing higher-than-expected return rates on electronics. How would you approach this as a data problem?" No predefined answer, they want a structured problem-solving approach. I went: define success metric, identify data sources, form hypotheses, prioritize by likelihood and testability, propose A/B test or analysis approach. They kept asking "what else would you need to know?"
Stats/ML round. Two questions: one on experimental design (how do you handle SUTVA violations in a store-level test?), one on model selection (logistic regression vs. gradient boosting for churn, when would you pick one over the other). Not deep ML theory but definitely stats-grounded.
Overall: more rigorous than I expected. Know SQL cold, know your experimental design, and have a structured framework for messy business questions.