Easy interview questions in Monitoring & SRE
What defines toil, with an example?
Define toil as manual, repetitive, automatable, tactical, no-enduring-value, scaling-with-growth work; distinguish it from overhead; give a concrete example.
SLI vs SLO vs SLA: how do they relate?
SLI is a measured metric, SLO is the internal target for that metric, SLA is the external contract with consequences.
How do SRE and DevOps relate?
DevOps is a broad culture of breaking down silos; SRE is one prescriptive way to do it with specific practices.
Explain the three pillars of observability
Metrics are cheap aggregated time series for detecting and alerting, logs are discrete event records for detail and context, traces follow one request across services to localize latency.
What are the Four Golden Signals?
Name latency, traffic, errors, and saturation; explain each briefly; describe measuring latency as a distribution separating success from failure.
Relationship between SLI, SLO, and SLA
SLI is the measured metric, SLO is the internal target for that metric, SLA is the external contract with consequences.
What is an error budget?
Error budget is one minus the SLO, the allowed unreliability; it gates feature velocity versus reliability work.
Proposing availability and latency SLIs for an auth API
Availability as the ratio of successful valid requests; latency as the fraction served under a threshold; measure at the edge from the user's view.
The three pillars of observability
Metrics show what and when via cheap aggregates, logs give detailed per-event context, traces show where across services.
Structured vs unstructured logging
Unstructured logs are free-text lines; structured logs are machine-readable key-value or JSON, enabling reliable parsing, filtering, and aggregation.
Essential tags for a request latency metric
Add method, route template, status code, and maybe service or region; they enable slicing while staying low-cardinality.
Core components of Prometheus
Server scrapes targets found via service discovery, stores samples in a local time-series database, with Alertmanager and exporters as helpers.
Symptom-based versus cause-based alerting
Symptom alerts fire on user impact like high error rate or latency; cause alerts fire on internal conditions like high CPU. Page on symptoms, treat causes as diagnostic.
First steps on a p99 latency page
Confirm scope and blast radius, check recent changes and deploys, then look at dependencies and resource saturation.
Triaging a 5xx error spike
Confirm impact and scope, declare and assign roles, check recent changes, stop the bleeding before root cause.
Primary goal and sections of a post-mortem
Goal is organizational learning and prevention, not blame; include summary, timeline, impact, root cause, action items.
Essential sections of a post-mortem
Summary, impact, timeline, root cause, lessons, and owned action items, each with a clear purpose.
The 5 Whys root cause technique
Repeatedly ask why to move from symptom to systemic cause, stop at an actionable systemic fix.
Why blameless culture matters for reviews
Blame causes people to hide facts, so reviews miss systemic causes; blamelessness surfaces honest detail.
Automating a recurring manual cache clear
Recognize the repetitive manual task, document the runbook, then automate it into the deploy pipeline as a post-deploy hook with monitoring.
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