Explain RED vs USE Metrics.
RED measures request performance (Rate, Errors, Duration), while USE measures resource health (Utilization, Saturation, Errors)—together they give complete observability. (#definition)
When to Use
Use RED for monitoring microservices and APIs to track user-facing issues like latency and errors. Use USE for infrastructure like servers, databases, and containers to detect resource bottlenecks and capacity problems.
Example
If your checkout API shows a high error rate in RED, USE metrics may reveal CPU saturation on the underlying server.
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Why Is It Important
RED highlights customer pain points, while USE helps diagnose root causes.
Combining them improves Mean Time to Detect (MTTD) and Mean Time to Resolve (MTTR).
Interview Tips
In interviews, define both clearly.
Explain that RED shows symptoms while USE identifies causes. Use a simple microservice example and mention percentiles, error budgets, and queues.
Trade-offs
RED is simpler and user-focused but misses low-level bottlenecks. USE provides depth but can overwhelm with noisy data. Using both ensures coverage at the cost of higher complexity.
Pitfalls
Common mistakes include relying on averages instead of percentiles, ignoring queue length, or tracking utilization without considering saturation and headroom.
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