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Reliability Observability and Incident Response Questions

Covers designing, building, and operating systems to be reliable, observable, and resilient, together with the operational practices for detecting, responding to, and learning from incidents. Instrumentation and observability topics include selecting and defining meaningful metrics and service level objectives and service level agreements, time series collection, dashboards, structured and contextual logs, distributed tracing, and sampling strategies. Monitoring and alerting topics cover setting effective alert thresholds to avoid alert fatigue, anomaly detection, alert routing and escalation, and designing signals that indicate degraded operation or regional failures. Reliability and fault tolerance topics include redundancy, replication, retries with idempotency, circuit breakers, bulkheads, graceful degradation, health checks, automatic failover, canary deployments, progressive rollbacks, capacity planning, disaster recovery and business continuity planning, backups, and data integrity practices such as validation and safe retry semantics. Operational and incident response practices include on call practices, runbooks and runbook automation, incident command and coordination, containment and mitigation steps, root cause analysis and blameless post mortems, tracking and implementing action items, chaos engineering and fault injection to validate resilience, and continuous improvement and cultural practices that support rapid recovery and learning. Candidates are expected to reason about trade offs between reliability, velocity, and cost and to describe architectural and operational patterns that enable rapid diagnosis, safe deployments, and operability at scale.

MediumSystem Design
64 practiced
Design a circuit-breaker pattern for a downstream data sink that intermittently returns HTTP 5xx errors, used by many concurrent ingestion workers. Specify states, thresholds for opening/closing the circuit, reset policy, integration with backoff retries, and how you would surface circuit status in metrics and alerts.
HardSystem Design
69 practiced
Design CI tests and deployment strategy to support schema evolution and contract testing for producer and consumer teams using Avro or Protobuf schemas. Include steps for backward/forward compatibility checks, automated consumer-driven contract tests, canary schema rollout, and migration patterns for incompatible changes.
MediumTechnical
67 practiced
You are receiving many noisy alerts from a downstream pipeline that experiences transient midnight spikes due to scheduled upstream loads. Propose a concrete alert tuning strategy that avoids alert fatigue while still detecting real outages or regressions. Include thresholding, aggregation windows, multi-signal alert rules, and escalation behavior.
HardTechnical
50 practiced
Your observability bill just spiked due to high-volume logs and traces. Propose an immediate and medium-term plan to reduce cost without sacrificing critical visibility. Cover retention policies, sampling, tiered storage, log aggregation, indexing choices, and SLO-driven retention.
HardSystem Design
63 practiced
Design a scalable observability architecture for a company-wide data platform processing 100k events per second and storing multiple petabytes per day. Cover collection, storage, query, retention policies for metrics/logs/traces, multi-tenant isolation, cost-control, schema for observability events, and privacy controls for PII in telemetry.

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