Explain the RED method for service dashboards.
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Quick Answer
RED = Rate, Errors, Duration — the three signals that answer 'is this service up and fast?'.
Detailed Answer
For request-driven services, chart the request Rate, the Error rate (e.g. 5xx share), and Duration (latency percentiles via histogram_quantile). RED complements USE (Utilization, Saturation, Errors) which suits resources like CPU and queues. Starting every service dashboard from RED gives on-call a consistent first screen.
Code Example
histogram_quantile(0.99, sum by (le) (rate(http_request_duration_seconds_bucket[$__rate_interval])))
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Interview Tip
Contrast RED (services) with USE (resources).
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