Stop Guessing: Using Error Budgets to Drive Engineering Decisions

​"Is the system up?" is the wrong question. The right question is: "Is the system reliable enough for our users?"
​In SRE, we use Error Budgets to turn a subjective conversation about "stability" into a data-driven decision.
​The Math of Reliability
If your Service Level Objective (SLO) is 99.9%, your error budget is 0.1%.
​Total uptime allowed: ~43 minutes of downtime per month.
​How to use the budget:
​If the budget is full: The team can take risks, ship experimental features, and move fast.
​If the budget is exhausted: Feature work stops. All hands move to reliability, bug fixes, and technical debt.
​Key Takeaway:
Error budgets aren't just a metric; they are a policy tool that bridges the gap between the "move fast" mentality of developers and the "don't break it" mentality of operations.