The 5-15% Rule
Infrastructure (cloud, tools, CI/CD, monitoring) should be 5-15% of total engineering budget. Below 5%: you're under-investing in developer experience. Above 15%: you're over-provisioning or using wrong services.
Common overspend causes: production-grade infrastructure in staging/dev (use smaller instances), unused resources nobody decommissioned, enterprise tools when open-source alternatives work, and over-provisioned databases "just in case."