Introduction to SRE

1 - What is SRE?

1.1 Definition

"SRE is what happens when you ask a software engineer to design an operations function." - Ben Treynor, Google

Site Reliability Engineering = Applying software engineering principles to infrastructure and operations.

1.2 Origins

Year	Event
2003	The first SRE team is created at Google
2004	Ben Treynor defines the principles
2016	Publication of the book "Site Reliability Engineering"
2018	Publication of the "SRE Workbook"
2020+	Widespread adoption across the industry

2 - SRE vs DevOps

2.1 Comparison

Aspect	DevOps	SRE
Nature	Culture/Movement	Implementation/Job
Focus	Collaboration	Reliability
Metrics	Variable	SLIs/SLOs
Background	Ops → Dev	Dev → Ops
Automation	Important	Fundamental

2.2 Complementarity

"Class SRE implements interface DevOps" - Google

SRE is a concrete way to implement DevOps with specific practices.

3 - Fundamental principles

3.1 The 7 SRE principles

sre_principles:
  1_operations_is_software:
    description: "Treat ops problems as software problems"
    example: "Automate instead of doing it manually"
    
  2_slos_not_features:
    description: "Reliability is a feature"
    example: "Prioritize stability over new features"
    
  3_work_to_minimize_toil:
    description: "Eliminate repetitive manual work"
    example: "Automate recurring tasks"
    
  4_automate_this_years_job_away:
    description: "Automate to free up time"
    example: "Scripts, tools, self-healing"
    
  5_move_fast_by_reducing_cost_of_failure:
    description: "Reducing the cost of errors lets you move faster"
    example: "Canary deployments, fast rollbacks"
    
  6_share_ownership_with_developers:
    description: "Shared responsibility"
    example: "Devs participate in on-call"
    
  7_use_same_tooling:
    description: "Same tools for Dev and SRE"
    example: "Monitoring, deployment pipelines"

3.2 The 50% rule

Goal: Maximum 50% of time on operations, minimum 50% on engineering.

4 - The role of an SRE

4.1 Responsibilities

Domain	Activities
Availability	SLOs, monitoring, alerting
Latency	Performance optimization
Performance	Load testing, profiling
Efficiency	Resource optimization
Change Management	Release engineering
Monitoring	Observability stack
Emergency Response	Incident management
Capacity Planning	Forecasting, scaling

4.2 Required skills

skills:
  technical:
    - Programming (Python, Go)
    - Linux/Unix systems
    - Networking
    - Cloud platforms
    - Kubernetes
    - Monitoring tools
    
  soft:
    - Problem solving
    - Communication
    - Collaboration
    - Decision making under pressure
    - Documentation

5 - SRE team structure

5.1 Models

5.2 Recommended ratios

Service type	Dev:SRE ratio
Critical services	6-8:1
Standard services	10-12:1
Mature services	20:1

6 - SRE Engagement

6.1 Production Readiness Review (PRR)

prr_checklist:
  architecture:
    - [ ] Design doc reviewed
    - [ ] Dependencies documented
    - [ ] Failure modes identified
    
  monitoring:
    - [ ] SLIs defined
    - [ ] SLOs agreed
    - [ ] Dashboards created
    - [ ] Alerts configured
    
  operations:
    - [ ] Runbooks written
    - [ ] On-call training done
    - [ ] Escalation path defined
    
  capacity:
    - [ ] Load tested
    - [ ] Scaling strategy defined
    - [ ] Resource limits set

6.2 Engagement criteria

engagement_criteria:
  minimum_requirements:
    - SLOs defined and measured
    - Error budget policy agreed
    - Monitoring in place
    - Documentation complete
    - On-call rotation shared
    
  exit_criteria:
    - Service stable for 6 months
    - Dev team trained
    - Toil below threshold
    - Error budget healthy

7 - SRE Culture

7.1 Blameless Culture

blameless_principles:
  - Focus on systems, not people
  - Ask "what" not "who"
  - Learn from failures
  - Share learnings openly
  - Encourage experimentation

7.2 Psychological Safety

Behavior	Encourages
"Naive" questions	Innovation
Admitting mistakes	Improvement
Asking for help	Collaboration
Challenging the status quo	Excellence

Summary

In this chapter, we discovered:

The definition of SRE
The difference with DevOps
The 7 fundamental principles
The role of an SRE
The team structures
The blameless culture

Next step

In the next chapter, we will look at SLIs, SLOs, and SLAs.

→ Next chapter: SLIs, SLOs, and SLAs

← Back to table of contents

1 - What is SRE?​

1.1 Definition​

1.2 Origins​

2 - SRE vs DevOps​

2.1 Comparison​

2.2 Complementarity​

3 - Fundamental principles​

3.1 The 7 SRE principles​

3.2 The 50% rule​

4 - The role of an SRE​

4.1 Responsibilities​

4.2 Required skills​

5 - SRE team structure​

5.1 Models​

5.2 Recommended ratios​

6 - SRE Engagement​

6.1 Production Readiness Review (PRR)​

6.2 Engagement criteria​

7 - SRE Culture​

7.1 Blameless Culture​

7.2 Psychological Safety​

Summary​

Next step​