The Ratio Question
Google's guideline: 1 SRE per 5-10 developers for mature services. Reality for most: 1 SRE per 15-20 developers is common but leads to reliability debt.
Under-staffed SRE costs: more incidents (each costing $10K-500K), slower incident recovery, burn-out and attrition ($200-400K per departure), and reliability debt that compounds.
Right-size by: services per SRE (max 5-7), on-call rotation (min 5 people), toil budget (<50% of time), and automation investment (30%+ of time).