Join sessions and messages to find time to first action

Last updated: August 10, 2025

Quick Overview

Write a query joining sessions and rides to produce the combined time to first action.

Airbnb

Data Manipulation (SQL/Python)

Data Scientist

Airbnb

August 10, 2025

Data Scientist

Onsite

Data Manipulation (SQL/Python)

Hard

124

2,291 solved

Write a query joining sessions and rides to produce the combined time to first action.

Airbnb 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

Data cleaning and transformation

Aggregate functions and GROUP BY

Index optimization and query performance

NULL handling and COALESCE

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

Can you rewrite this without using subqueries?
How would you validate the correctness of your query results?
What indexes would you create to support this query?

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Practice SQL Problems

Sample Answer

Problem Understanding

To solve the problem, we need to analyze the data from two tables: sessions and messages. The sessions table contains records of user sessions, including user IDs and timestamps when each sessio...

Approach

Identify Keys: Determine the primary keys in both tables for joining. Typically, the sessions table will have a session_id and the messages table will have a message_id along with a `se...

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Airbnb Data Scientist Interview Guide

Interview process, tips, and preparation timeline