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HLDsystem_design~12 mins

SLA, SLO, and SLI definitions in HLD - Architecture Diagram

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System Overview - SLA, SLO, and SLI definitions

This system explains the relationship between SLA, SLO, and SLI in service reliability. It helps teams set clear expectations and measure service quality to keep users happy.

Architecture Diagram
User
  |
  v
Service Level Agreement (SLA)
  |
  v
Service Level Objective (SLO)
  |
  v
Service Level Indicator (SLI)
  |
  v
Monitoring & Reporting System
  |
  v
Feedback Loop to Improve Service
Components
User
actor
Person or system using the service and expecting reliability
Service Level Agreement (SLA)
agreement
Formal contract defining expected service quality and penalties
Service Level Objective (SLO)
objective
Specific measurable goals derived from SLA to guide service performance
Service Level Indicator (SLI)
metric
Quantitative measure of service performance (e.g., uptime, latency)
Monitoring & Reporting System
service
Collects SLIs and reports if SLOs are met
Feedback Loop to Improve Service
process
Uses monitoring data to improve service and meet SLAs
Request Flow - 6 Hops
User → Service Level Agreement (SLA)
Service Level Agreement (SLA) → Service Level Objective (SLO)
Service Level Objective (SLO) → Service Level Indicator (SLI)
Service Level Indicator (SLI) → Monitoring & Reporting System
Monitoring & Reporting System → Feedback Loop to Improve Service
Feedback Loop to Improve Service → Service Level Agreement (SLA)
Failure Scenario
Component Fails:Monitoring & Reporting System
Impact:SLI data is not collected or reported, so SLO compliance is unknown, risking SLA breaches without detection
Mitigation:Use redundant monitoring systems and alert on monitoring failures to restore visibility quickly
Architecture Quiz - 3 Questions
Test your understanding
What does an SLI represent in this system?
AA formal contract with the user
BA process to improve the service
CA measurable metric of service performance
DA specific goal derived from the SLA
Design Principle
This architecture clearly separates expectations (SLA), goals (SLO), and measurements (SLI) with a monitoring system to ensure service reliability and continuous improvement.