SRE — Site Reliability Engineering Principles

Site Reliability Engineering balances innovation with reliability through data-driven practices.

Introduction

SRE applies engineering principles to operations, emphasizing reliability, automation, and continuous improvement.

• SRE — Site Reliability Engineering Principles
• Core Concepts
• SLIs (Service Level Indicators)
• SLOs (Service Level Objectives)
• Error Budget
• Practices
• Monitoring and Alerting
• Toil Reduction
• Blameless Postmortems
• FAQ

Core Concepts

SLIs (Service Level Indicators)

Measurable aspects of service:

• Availability (uptime %)
• Latency (response time p99)
• Error rate
• Throughput

SLI = successful_requests / total_requests * 100

SLOs (Service Level Objectives)

Targets for SLIs:

• Availability SLO: 99.9% uptime
• Latency SLO: p99 < 500ms
• Error rate SLO: < 0.1%

Error Budget

Resources available for failures:

Error Budget = (1 - SLO) * Time Period
100% - 99.9% = 0.1% = 43 minutes per month

Use budget to prioritize features vs reliability.

Practices

Monitoring and Alerting

Alert when → SLI approaching SLO violation
Don't alert on → predicted violations beyond error budget

Toil Reduction

Identify repetitive operational tasks and automate:

Manual deployments → CI/CD pipeline
Manual scaling → Auto-scaling
Manual backups → Automated backups

Blameless Postmortems

After incidents:

1. Understand what happened
2. Identify contributing factors
3. Improve systems
4. No blame assignment

FAQ

Q: What's a reasonable SLO? A: Depends on service. Typical: 99% (critical), 99.5% (important), 95% (internal).

Q: How do I reduce toil? A: Track manual tasks, prioritize high-frequency items, automate progressively.