FinOps for SREs: Cutting Costs Without Breaking Things

An SRE at a major Korean tech company describes an SRE-driven FinOps approach that prioritizes SLO protection and error budgets before any AWS cost optimization. The methodology includes three guarantees—error budget protection, assured minimum downtime, and reliability over savings—and identified $48-67K/year in savings across four AWS accounts. The workflow is supported by an open-source CLI tool called aws-finops-toolkit and is structured as a multi-part series covering pre-flight analysis, passive waste removal, and active downsizing with SRE guardrails.