Design a DAU/MAU metrics system
Company: Vanta
Role: Software Engineer
Category: System Design
Difficulty: medium
Interview Round: Onsite
Design a system to compute and serve product engagement metrics:
- **DAU**: Daily Active Users
- **MAU**: Monthly Active Users
Assume an "active user" means a distinct user who performed at least one qualifying event (e.g., app open, page view, session start) within the time window.
Your design should cover:
- Event ingestion and data modeling (what fields are required)
- De-duplication and identity (user_id, device_id, logged-out users)
- Computing DAU/MAU accurately (time zones, late events, backfills)
- Storage/compute choices for large scale
- Serving queries/dashboards (latency, caching, correctness guarantees)
- Monitoring, data quality, and privacy considerations
Quick Answer: This question evaluates a candidate's ability to design scalable analytics and engagement-metrics pipelines, including event ingestion, de-duplication and identity resolution, time-window correctness for DAU/MAU, storage and compute trade-offs, serving latency/caching, and monitoring/privacy considerations.