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Google·Software Engineer·Onsite - System Design / Architecture·Senior

Senior
Jun 2026

Summary

Google data engineer interview with a system design round focused on warehousing for a ride-sharing product. Pretty classic schema design territory but the scope kept expanding mid-question which threw me off a bit.

Questions Asked (1)

Q1

Design a data warehouse schema for a ride-sharing service.

Data ModelingSystem DesignTechnical Trade-offs
Author's notes

I started with a star schema, trips as the fact table, dimensions for drivers, riders, locations, time.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the business goals and key metrics (e.g., trip analysis, driver performance, pricing) to determine the required facts and dimensions. Then propose a dimensional model (star schema) with a central fact table for trips and supporting dimensions, explaining how it supports analytical queries. Finally, discuss trade-offs like normalization vs. denormalization, partitioning, and scalability.

Pro tip: Emphasize that the schema should be optimized for query performance and scalability, and mention how you would handle slowly changing dimensions (SCDs) for entities like drivers and riders to maintain historical accuracy.

1. Clarify Requirements

Ask about the key business questions and metrics (e.g., trip counts, revenue, driver utilization) to ensure the schema supports them.

2. Identify Facts and Dimensions

Determine the central fact table (e.g., trips) and the dimensions (e.g., time, location, driver, rider, payment) that provide context.

3. Design the Schema

Propose a star schema with a fact table containing foreign keys to dimensions and additive measures like fare and distance.

4. Address Slowly Changing Dimensions

Explain how to handle changes in dimension attributes (e.g., driver's rating) using SCD Type 2 to preserve history.

5. Discuss Trade-offs and Scalability

Talk about partitioning the fact table by date, indexing strategies, and potential use of columnar storage for performance.

Key Points to Mention

  • Star schema vs. snowflake schema and why star is preferred for analytical queries
  • Grain of the fact table (e.g., one row per trip) and additive vs. semi-additive measures
  • Handling of slowly changing dimensions (SCD Type 2) for drivers and riders
  • Partitioning and indexing strategies for large fact tables
  • Integration with real-time data and lambda architecture for up-to-date analytics
  • Data governance, security, and privacy considerations for PII

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