Context

At Didi Chuxing, product performance can be measured from several sources such as Didi App event logs, order transaction tables, and dashboard rollups. These sources often disagree because they differ in latency, granularity, and business logic.

Core question

Explain how you would prioritize data sources when analyzing product performance. Your answer should cover:

1. How you decide which source should be the source of truth for a metric
2. How SQL can be used to compare completeness, freshness, and consistency across sources
3. How you would handle conflicts between event-level data and aggregated reporting tables
4. What trade-offs you would communicate to stakeholders before sharing results

Scope guidance

The interviewer is not looking for a single “correct” source. They want a structured framework for choosing among sources, plus a practical explanation of how you would validate that choice with SQL checks and basic aggregations.