Join clicks and products to find DAU/MAU ratio
Last updated: November 20, 2025
Quick Overview
Write a query joining clicks and events to produce the combined DAU/MAU ratio.
Expedia
November 20, 2025186
7
3,356 solved
Write a query joining clicks and events to produce the combined DAU/MAU ratio.
Expedia asks this during the Onsite because data engineering skills are critical for the role. You should be comfortable with complex joins, window functions, CTEs, and performance optimization.
What the Interviewer Expects
- Solve complex analytical problems with elegant, readable SQL
- Optimize queries for large-scale datasets with partitioning and indexing
- Use recursive CTEs, lateral joins, and advanced window functions
- Design the data model alongside the query solution
- Discuss trade-offs between SQL and programmatic approaches (Python/pandas)
- Consider the operational aspects: query scheduling, incremental processing
Key Topics to Cover
How to Approach This
- Clarify the schema and expected output format before writing queries.
- Use CTEs (WITH clauses) to break complex queries into readable steps.
- Consider window functions (ROW_NUMBER, RANK, LAG, LEAD) for ranking and sequential analysis.
- Watch for NULLs, duplicates, and edge cases in JOINs and GROUP BY.
- For pandas, prefer vectorized operations over row-by-row iteration.
Possible Follow-up Questions
- What would you do if this query needs to run every 5 minutes?
- How would you optimize this query for a table with 100 million rows?
- How would you handle this if the data was spread across multiple databases?
- What indexes would you create to support this query?
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