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

Reading isn't practice. Get AI feedback on your answers.

Other Companies

Wayfair Data Engineer Interview Questions

Reading isn't practice. Get AI feedback on your answers.

Other Companies