· Palaniappan P
· 5 min read
Designing a Customer-Facing SLA on AWS (2026): SLO Error Budgets and the Composite-Availability Math Most Teams Skip
A stack of ALB + EC2 + RDS Multi-AZ + S3 composes to ~99.83% availability—so promising customers 99.9% is a check you cannot cash. This guide does the composition math, converts it to an error budget (99.9% = 43.2 min/month), and shows why AWS service credits never fund your SLA penalties.