Quality Attributes

The "-ilities": taxonomy, selection, measurement, governance

Cost as first-class quality attribute; five cost dimensions (build/run/change/downtime/opportunity); architecture style as dominant cost driver; ROI patterns (deployment automation 18×, observability, stability patterns); common cost traps; cost-vs-other-ilities trade-offs

*Fundamentals of Software Architecture* — Richards & Ford

definition; replication vs optimization strategies; scale up vs scale out; stateless services requirement; Amdahl's Law; hyperscale; quality attribute trade-offs (performance, availability, security, manageability); architecture evolution pattern