Explain SLI/SLO/SLA and design monitoring

Quick Overview

This question evaluates a candidate's competency in service reliability and observability, specifically understanding and distinguishing SLIs, SLOs, and SLAs, planning error budgets, and designing monitoring and alerting for a production web API.

SLI vs SLO vs SLA for a Web API; Error Budgets; Monitoring and Alerting Design

Context: You are designing reliability goals and on-call policies for a production web API that serves JSON over HTTPS. Requests include a mix of GET/POST endpoints. You need to define what you measure (SLIs), targets (SLOs), the contractual promise (SLA), plan an error budget for a quarterly SLO, and design monitoring/alerting that minimizes alert fatigue.

Tasks

Define and contrast SLI, SLO, and SLA. Give concrete SLI examples for:
- Availability (success rate)
- Latency (e.g., request duration under a threshold)
Given a quarterly target SLO, define a reasonable error budget, and show how you would apportion and track its consumption over time.
Design a monitoring and alerting system that minimizes alert fatigue:
- Choose which signals to alert on and why
- Set alert thresholds relative to SLOs
- Aggregate and deduplicate alerts
- Apply multi-window/multi-burn-rate policies
- Define escalation, silencing, and runbook practices

Explain SLI/SLO/SLA and design monitoring

Quick Overview