What are the four golden signals, and why are they useful for monitoring?
What the interviewer wants to hear
- Latency, including separating successful and failed requests
- Traffic or demand
- Errors, explicit and implicit
- Saturation, how full the service is
- Focus on user-visible symptoms
Model answer
The four golden signals are latency, traffic, errors and saturation. Latency is how long requests take, and I track percentiles like p50 and p99, keeping successful and failed requests separate because fast errors can make latency look good. Traffic is the demand on the system, such as requests per second. Errors are the rate of failed requests, including implicit failures like a 200 response with wrong content or a response that breaks the SLO. Saturation is how full the service is, for example CPU, memory, queue length or connection pool use. They are useful because they focus on what users experience and give a small, consistent starting point for dashboards and alerts across every service.
Can you answer it under time pressure?
Take a timed easy round and get scored on every answer.
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