Question 1

Describe your role in a team project.

Accepted Answer

Situation: Our org adopted a data mesh; we needed to prove the model with a first domain. Task: Lead the Orders domain as the first production deployment. Action: I designed the domain's data contracts, implemented ingestion and transformation pipelines (Spark/Delta), and set up the serving layer (Athena). I collaborated with the central platform team on governance, security, and discovery. I mentored other domain teams on patterns and runbooks....

Question 2

Calculate the total number of transactions (units sold) for each product.

Accepted Answer

**SQL**: SELECT product_id, SUM(units_sold) AS total_units FROM transactions GROUP BY product_id. **With product name**: JOIN products. **Spark**: df.groupBy('product_id').agg(F.sum('units_sold').alias('total_units'))....

Question 3

Design a structure (data model) that allows efficient querying of movies based on multiple search criteria (title, genre, actor, director).

Accepted Answer

**Section 1 — The Context (The 'Why')**
The primary challenge for this design in SQL is balancing scale, cost, and reliability. At scale, naive approaches fail: single points of failure cause cascades, schema evolution breaks consumers, and over-provisioning explodes cost. Failure modes include silent data loss from non-idempotent writes, cascading job failures from tight coupling, and operational burden from manual intervention....

Question 4

Write a query to identify unique user sessions.

Accepted Answer

If session_id exists: SELECT COUNT(DISTINCT session_id) AS unique_sessions FROM user_events. For session logic (30-min inactivity): Use LAG + CASE for session boundaries; SUM(session_flag) OVER (PARTITION BY user_id ORDER BY event_time) AS session_id. **Why**: Define session (time-based, event-based) consistently....

Wayfair Data Engineer Interview Questions

+1 More Questions with Expert Answers

Other Companies