Logging & Observability interview question · Most asked
What are the RED, USE and Four Golden Signals methods?
Summary
They're checklists for what to measure: RED (Rate, Errors, Duration) for request-driven services; USE (Utilization, Saturation, Errors) for resources like CPU, disks and pools; and Google's Four Golden Signals (latency, traffic, errors, saturation) for user-facing systems.
Longer Answer
RED gives a consistent dashboard per service and endpoint. USE helps find resource bottlenecks (a DB connection pool at 100% utilization with a growing wait queue is saturated). Golden Signals combine both views. Measure latency as percentiles (p50, p95, p99), not averages, and separate successful from failed request latency.
Key Points
- RED for services
- USE for resources
- Golden signals for user-facing systems
- Percentiles, not averages
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