What Is Site Reliability Engineering?
Site Reliability Engineering — SRE — emerged at Google as a way to run large-scale systems sustainably. Instead of treating operations as a separate discipline from development, SRE applies engineering thinking to reliability problems. This approach has spread across the industry because it works.
The SRE Philosophy
Traditional operations teams often find themselves in conflict with development teams. Developers want to ship features quickly; operations wants stability. SRE resolves this tension by treating reliability as a feature that can be measured, budgeted, and engineered like any other.
The core insight is that 100% reliability is neither achievable nor desirable. Users can't tell the difference between 99.99% and 100% availability, but the engineering cost difference is enormous. SRE embraces this reality and makes explicit decisions about acceptable reliability levels.
Core Principles
Measure everything. You can't improve what you don't measure. SRE teams define clear metrics for system health and track them continuously. Decisions come from data, not gut feelings.
Automate toil. Repetitive manual work — called "toil" — doesn't scale and burns out engineers. SRE prioritizes automating operational tasks so humans focus on improvements rather than maintenance.
Accept that failures happen. Instead of pretending systems won't fail, SRE plans for failure. This means building redundancy, practicing incident response, and learning from every outage.
Error budgets guide decisions. If a service has budget remaining for acceptable downtime, ship features. If the budget is exhausted, focus on reliability. This creates objective criteria for release decisions.
SRE vs Traditional Operations
The difference between SRE and traditional operations isn't just terminology — it's a fundamental shift in approach.
Traditional operations tends toward manual processes — runbooks that humans follow step by step. SRE prefers automated solutions that handle routine situations without human intervention.
Traditional operations is often reactive firefighting — responding to problems as they occur. SRE emphasizes proactive reliability — identifying and fixing weaknesses before they cause outages.
The traditional mindset is "keep it running." The SRE mindset is "engineer reliability" — treating operational concerns with the same rigor as feature development.
Who Does SRE?
Some organizations have dedicated SRE teams. Others embed SRE practices within development teams. The specific structure matters less than adopting the principles: measuring reliability, automating operations, and making data-driven decisions about acceptable risk.
SRE isn't just for massive scale. The principles apply whether you're running a small startup or a global platform. Start with clear reliability goals and build from there.