Tools / Datadog Interview questions
When should you use an outlier monitor versus a threshold monitor?
Use a threshold monitor when you know the exact acceptable value in advance and it's the same for every entity being monitored - like 'any host with disk usage over 90% is a problem,' regardless of how its peers are doing.
Use an outlier monitor when 'normal' genuinely differs across a group and what matters is relative deviation from peers, not an absolute number - like catching one host in a fleet of similar hosts whose latency has drifted noticeably higher than the rest, even if that latency alone wouldn't cross any fixed threshold.
A practical tell: if you'd have to keep manually tuning a threshold per-host to avoid false alarms because 'normal' varies so much between them, that's usually a sign an outlier monitor is the better fit for that specific metric.
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