Intermediate interview questions in Monitoring & SRE, page 3
Mitigating risk from an unproven external dependency?
Timeouts and circuit breakers to fail fast, bulkheads to isolate resources, fallbacks or cached/degraded responses.
Zero-downtime index migration on a hot table?
Build the index concurrently to avoid table locks, run off-peak with monitoring, and keep it reversible since dropping an index is cheap.
How do you run your first production chaos experiment?
Pick a low-risk known weakness, define a measurable hypothesis, brief stakeholders and on-call, run small with an abort, then analyze and fix.
Why does 200ms latency drop requests? Diagnose it.
Little's Law shows added latency raises in-flight requests, exhausting the thread or connection pool; check pool saturation, timeouts, and retries.
Resource faults versus network faults: when each matters?
Resource faults probe local saturation and autoscaling; network faults probe distributed-call resilience like timeouts and retries.
Automating chaos in CI/CD for continuous verification?
Run codified experiments against staging or canary with pass/fail on steady-state SLIs; prerequisites are observability, automated abort, and isolation.
A team keeps blowing its error budget. First steps?
Analyze where the budget is burning via SLIs and postmortems, validate the SLO and SLIs are sound, then partner blamelessly on the top fixes.
Embedded vs consulting SRE engagement models
Embedded SREs sit inside one team for deep impact but limited reach; consulting SREs advise many teams broadly but shallowly.
Conducting a Production Readiness Review
Assess monitoring and alerting, capacity and load testing, failure modes and dependencies, on-call and runbooks, and rollback or release safety.
Keeping a postmortem blameless after an admission
Acknowledge the courage, redirect from who to why the system allowed it, ask what guardrails were missing.
Calculating downtime for a 99.9% SLO
0.1% of 30 days is roughly 43 minutes of allowed downtime; healthy budget enables faster shipping while depletion slows or freezes deploys.
Writing high-quality postmortem action items
Good action items are specific, assigned to an owner, prioritized, tracked to completion, and ideally prevent recurrence rather than just detect faster.
Rolling update vs blue-green deployment
Rolling replaces instances gradually with minimal extra capacity but mixes versions; blue-green runs two full environments for instant switch and rollback at double the cost.
Designing shallow vs deep health checks
Shallow checks confirm the process is alive; deep checks verify dependencies; use shallow for liveness/load-balancer routing and deep sparingly to avoid…
First-SRE 90-day plan at a startup
Listen and measure first, pick one high-impact service, define SLIs/SLOs and basic alerting, then show reduced toil or incidents to leadership.
OpenTelemetry agent and gateway architecture
Agents run per-node for local collection and host enrichment; gateways are central, horizontally scaled pools for batching, tail sampling, and routing.
Key roles in incident response
Incident Commander coordinates and decides but does not fix; Communications Lead handles stakeholders; Operations/SMEs do hands-on diagnosis and remediation.
Breaking tunnel vision during an incident
Call out the assumption, ask for disconfirming evidence, list parallel hypotheses, split responders to investigate them, and anchor on what changed and the data.
Safeguards for automated remediation runbooks
Add rate limits and circuit breakers on restarts, escalate to humans after N attempts, log all actions, and check for cascading failure before acting.
Automating actions on error budget burn
Use multi-window burn-rate alerts; on fast burn, auto-trigger actions like halting deploys, rolling back, or scaling, with escalating tiers.
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