Design a metrics collection and alerting system
Company: Snapchat
Role: Software Engineer
Category: System Design
Difficulty: medium
Interview Round: Onsite
Design a metrics collection and alerting system (like a simplified monitoring platform).
Functional requirements:
- Collect time-series metrics from many services/hosts (e.g., counters, gauges, timers).
- Support **near real-time querying/dashboards** (low-latency queries over recent data).
- Support **offline/analytical queries** over long time ranges (heavier aggregations, historical analysis).
- Support **alerting**: user-defined rules (e.g., threshold, rate of change) with notifications.
Non-functional requirements:
- High write throughput, horizontal scalability, high availability.
- Handle spikes, backpressure, and partial failures.
- Reasonable multi-tenancy and access control.
Provide an end-to-end architecture, key data models, storage choices, and how alert evaluation works. Discuss tradeoffs (e.g., Lambda/Kappa style), retention, and handling high-cardinality metrics.
Overview: This question evaluates system design competencies such as scalable time-series data modeling, ingestion and storage architecture, query latency versus retention trade-offs, and alert evaluation logic within the System Design domain.
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